Index: include/unordered_map
===================================================================
--- include/unordered_map
+++ include/unordered_map
@@ -1345,6 +1345,67 @@
 #endif
 };
 
+#ifndef _LIBCPP_HAS_NO_DEDUCTION_GUIDES
+template<class _InputIterator,
+         class _Hash = hash<__iter_key_type<_InputIterator>>,
+         class _Pred = equal_to<__iter_key_type<_InputIterator>>,
+         class _Allocator = allocator<__iter_to_alloc_type<_InputIterator>>,
+         class = typename enable_if<!__is_allocator<_Hash>::value, void>::type,
+         class = typename enable_if<!is_integral<_Hash>::value, void>::type,
+         class = typename enable_if<!__is_allocator<_Pred>::value, void>::type,
+         class = typename enable_if<__is_allocator<_Allocator>::value, void>::type>
+unordered_map(_InputIterator, _InputIterator, typename allocator_traits<_Allocator>::size_type = 0,
+              _Hash = _Hash(), _Pred = _Pred(), _Allocator = _Allocator())
+  -> unordered_map<__iter_key_type<_InputIterator>, __iter_mapped_type<_InputIterator>, _Hash, _Pred, _Allocator>;
+
+template<class _Key, class _Tp, class _Hash = hash<_Key>,
+         class _Pred = equal_to<_Key>, class _Allocator = allocator<pair<const _Key, _Tp>>,
+         class = typename enable_if<!__is_allocator<_Hash>::value, void>::type,
+         class = typename enable_if<!is_integral<_Hash>::value, void>::type,
+         class = typename enable_if<!__is_allocator<_Pred>::value, void>::type,
+         class = typename enable_if<__is_allocator<_Allocator>::value, void>::type>
+unordered_map(initializer_list<pair<_Key, _Tp>>, typename allocator_traits<_Allocator>::size_type = 0,
+              _Hash = _Hash(), _Pred = _Pred(), _Allocator = _Allocator())
+  -> unordered_map<_Key, _Tp, _Hash, _Pred, _Allocator>;
+
+template<class _InputIterator, class _Allocator,
+         class = typename enable_if<__is_allocator<_Allocator>::value, void>::type>
+unordered_map(_InputIterator, _InputIterator, typename allocator_traits<_Allocator>::size_type, _Allocator)
+  -> unordered_map<__iter_key_type<_InputIterator>, __iter_mapped_type<_InputIterator>,
+                   hash<__iter_key_type<_InputIterator>>, equal_to<__iter_key_type<_InputIterator>>, _Allocator>;
+
+template<class _InputIterator, class _Allocator,
+         class = typename enable_if<__is_allocator<_Allocator>::value, void>::type>
+unordered_map(_InputIterator, _InputIterator, _Allocator)
+  -> unordered_map<__iter_key_type<_InputIterator>, __iter_mapped_type<_InputIterator>,
+                   hash<__iter_key_type<_InputIterator>>, equal_to<__iter_key_type<_InputIterator>>, _Allocator>;
+
+template<class _InputIterator, class _Hash, class _Allocator,
+         class = typename enable_if<!__is_allocator<_Hash>::value, void>::type,
+         class = typename enable_if<!is_integral<_Hash>::value, void>::type,
+         class = typename enable_if<__is_allocator<_Allocator>::value, void>::type>
+unordered_map(_InputIterator, _InputIterator, typename allocator_traits<_Allocator>::size_type, _Hash, _Allocator)
+  -> unordered_map<__iter_key_type<_InputIterator>, __iter_mapped_type<_InputIterator>,
+                   _Hash, equal_to<__iter_key_type<_InputIterator>>, _Allocator>;
+
+template<class _Key, class _Tp, class _Allocator,
+         class = typename enable_if<__is_allocator<_Allocator>::value, void>::type>
+unordered_map(initializer_list<pair<_Key, _Tp>>, typename allocator_traits<_Allocator>::size_type, _Allocator)
+  -> unordered_map<_Key, _Tp, hash<_Key>, equal_to<_Key>, _Allocator>;
+
+template<class _Key, class _Tp, class _Allocator,
+         class = typename enable_if<__is_allocator<_Allocator>::value, void>::type>
+unordered_map(initializer_list<pair<_Key, _Tp>>, _Allocator)
+  -> unordered_map<_Key, _Tp, hash<_Key>, equal_to<_Key>, _Allocator>;
+
+template<class _Key, class _Tp, class _Hash, class _Allocator,
+         class = typename enable_if<!__is_allocator<_Hash>::value, void>::type,
+         class = typename enable_if<!is_integral<_Hash>::value, void>::type,
+         class = typename enable_if<__is_allocator<_Allocator>::value, void>::type>
+unordered_map(initializer_list<pair<_Key, _Tp>>, typename allocator_traits<_Allocator>::size_type, _Hash, _Allocator)
+  -> unordered_map<_Key, _Tp, _Hash, equal_to<_Key>, _Allocator>;
+#endif
+
 template <class _Key, class _Tp, class _Hash, class _Pred, class _Alloc>
 unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>::unordered_map(
         size_type __n, const hasher& __hf, const key_equal& __eql)
@@ -2035,6 +2096,67 @@
 
 };
 
+#ifndef _LIBCPP_HAS_NO_DEDUCTION_GUIDES
+template<class _InputIterator,
+         class _Hash = hash<__iter_key_type<_InputIterator>>,
+         class _Pred = equal_to<__iter_key_type<_InputIterator>>,
+         class _Allocator = allocator<__iter_to_alloc_type<_InputIterator>>,
+         class = typename enable_if<!__is_allocator<_Hash>::value, void>::type,
+         class = typename enable_if<!is_integral<_Hash>::value, void>::type,
+         class = typename enable_if<!__is_allocator<_Pred>::value, void>::type,
+         class = typename enable_if<__is_allocator<_Allocator>::value, void>::type>
+unordered_multimap(_InputIterator, _InputIterator, typename allocator_traits<_Allocator>::size_type = 0,
+              _Hash = _Hash(), _Pred = _Pred(), _Allocator = _Allocator())
+  -> unordered_multimap<__iter_key_type<_InputIterator>, __iter_mapped_type<_InputIterator>, _Hash, _Pred, _Allocator>;
+
+template<class _Key, class _Tp, class _Hash = hash<_Key>,
+         class _Pred = equal_to<_Key>, class _Allocator = allocator<pair<const _Key, _Tp>>,
+         class = typename enable_if<!__is_allocator<_Hash>::value, void>::type,
+         class = typename enable_if<!is_integral<_Hash>::value, void>::type,
+         class = typename enable_if<!__is_allocator<_Pred>::value, void>::type,
+         class = typename enable_if<__is_allocator<_Allocator>::value, void>::type>
+unordered_multimap(initializer_list<pair<_Key, _Tp>>, typename allocator_traits<_Allocator>::size_type = 0,
+              _Hash = _Hash(), _Pred = _Pred(), _Allocator = _Allocator())
+  -> unordered_multimap<_Key, _Tp, _Hash, _Pred, _Allocator>;
+
+template<class _InputIterator, class _Allocator,
+         class = typename enable_if<__is_allocator<_Allocator>::value, void>::type>
+unordered_multimap(_InputIterator, _InputIterator, typename allocator_traits<_Allocator>::size_type, _Allocator)
+  -> unordered_multimap<__iter_key_type<_InputIterator>, __iter_mapped_type<_InputIterator>,
+                   hash<__iter_key_type<_InputIterator>>, equal_to<__iter_key_type<_InputIterator>>, _Allocator>;
+
+template<class _InputIterator, class _Allocator,
+         class = typename enable_if<__is_allocator<_Allocator>::value, void>::type>
+unordered_multimap(_InputIterator, _InputIterator, _Allocator)
+  -> unordered_multimap<__iter_key_type<_InputIterator>, __iter_mapped_type<_InputIterator>,
+                   hash<__iter_key_type<_InputIterator>>, equal_to<__iter_key_type<_InputIterator>>, _Allocator>;
+
+template<class _InputIterator, class _Hash, class _Allocator,
+         class = typename enable_if<!__is_allocator<_Hash>::value, void>::type,
+         class = typename enable_if<!is_integral<_Hash>::value, void>::type,
+         class = typename enable_if<__is_allocator<_Allocator>::value, void>::type>
+unordered_multimap(_InputIterator, _InputIterator, typename allocator_traits<_Allocator>::size_type, _Hash, _Allocator)
+  -> unordered_multimap<__iter_key_type<_InputIterator>, __iter_mapped_type<_InputIterator>,
+                   _Hash, equal_to<__iter_key_type<_InputIterator>>, _Allocator>;
+
+template<class _Key, class _Tp, class _Allocator,
+         class = typename enable_if<__is_allocator<_Allocator>::value, void>::type>
+unordered_multimap(initializer_list<pair<_Key, _Tp>>, typename allocator_traits<_Allocator>::size_type, _Allocator)
+  -> unordered_multimap<_Key, _Tp, hash<_Key>, equal_to<_Key>, _Allocator>;
+
+template<class _Key, class _Tp, class _Allocator,
+         class = typename enable_if<__is_allocator<_Allocator>::value, void>::type>
+unordered_multimap(initializer_list<pair<_Key, _Tp>>, _Allocator)
+  -> unordered_multimap<_Key, _Tp, hash<_Key>, equal_to<_Key>, _Allocator>;
+
+template<class _Key, class _Tp, class _Hash, class _Allocator,
+         class = typename enable_if<!__is_allocator<_Hash>::value, void>::type,
+         class = typename enable_if<!is_integral<_Hash>::value, void>::type,
+         class = typename enable_if<__is_allocator<_Allocator>::value, void>::type>
+unordered_multimap(initializer_list<pair<_Key, _Tp>>, typename allocator_traits<_Allocator>::size_type, _Hash, _Allocator)
+  -> unordered_multimap<_Key, _Tp, _Hash, equal_to<_Key>, _Allocator>;
+#endif
+
 template <class _Key, class _Tp, class _Hash, class _Pred, class _Alloc>
 unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>::unordered_multimap(
         size_type __n, const hasher& __hf, const key_equal& __eql)
Index: test/std/containers/unord/unord.map/unord.map.cnstr/deduct.fail.cpp
===================================================================
--- /dev/null
+++ test/std/containers/unord/unord.map/unord.map.cnstr/deduct.fail.cpp
@@ -0,0 +1,106 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// <unordered_map>
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+// UNSUPPORTED: libcpp-no-deduction-guides
+
+//  template<class InputIterator,
+//           class Hash = hash<iter-key-type<InputIterator>>,
+//           class Pred = equal_to<iter-key-type<InputIterator>>,
+//           class Allocator = allocator<iter-to-alloc-type<InputIterator>>>
+//  unordered_map(InputIterator, InputIterator, typename see below::size_type = see below,
+//                Hash = Hash(), Pred = Pred(), Allocator = Allocator())
+//    -> unordered_map<iter-key-type<InputIterator>, iter-mapped-type<InputIterator>, Hash, Pred,
+//                     Allocator>;
+//
+//  template<class Key, class T, class Hash = hash<Key>,
+//           class Pred = equal_to<Key>, class Allocator = allocator<pair<const Key, T>>>
+//  unordered_map(initializer_list<pair<Key, T>>,
+//                typename see below::size_type = see below, Hash = Hash(),
+//                Pred = Pred(), Allocator = Allocator())
+//    -> unordered_map<Key, T, Hash, Pred, Allocator>;
+//
+//  template<class InputIterator, class Allocator>
+//  unordered_map(InputIterator, InputIterator, typename see below::size_type, Allocator)
+//    -> unordered_map<iter-key-type<InputIterator>, iter-mapped-type<InputIterator>,
+//                     hash<iter-key-type<InputIterator>>,
+//                     equal_to<iter-key-type<InputIterator>>, Allocator>;
+//
+//  template<class InputIterator, class Allocator>
+//  unordered_map(InputIterator, InputIterator, Allocator)
+//    -> unordered_map<iter-key-type<InputIterator>, iter-mapped-type<InputIterator>,
+//                     hash<iter-key-type<InputIterator>>,
+//                     equal_to<iter-key-type<InputIterator>>, Allocator>;
+//
+//  template<class InputIterator, class Hash, class Allocator>
+//  unordered_map(InputIterator, InputIterator, typename see below::size_type, Hash, Allocator)
+//    -> unordered_map<iter-key-type<InputIterator>, iter-mapped-type<InputIterator>, Hash,
+//                     equal_to<iter-key-type<InputIterator>>, Allocator>;
+//
+//  template<class Key, class T, class Allocator>
+//  unordered_map(initializer_list<pair<Key, T>>, typename see below::size_type, Allocator)
+//    -> unordered_map<Key, T, hash<Key>, equal_to<Key>, Allocator>;
+//
+//  template<class Key, class T, class Allocator>
+//  unordered_map(initializer_list<pair<Key, T>>, Allocator)
+//    -> unordered_map<Key, T, hash<Key>, equal_to<Key>, Allocator>;
+//
+//  template<class Key, class T, class Hash, class Allocator>
+//  unordered_map(initializer_list<pair<Key, T>>, typename see below::size_type, Hash,
+//                Allocator)
+//    -> unordered_map<Key, T, Hash, equal_to<Key>, Allocator>;
+
+#include <climits> // INT_MAX
+#include <functional>
+#include <unordered_map>
+
+int main(int, char**)
+{
+    using P = std::pair<const int, int>;
+    {
+        // cannot deduce Key from nothing
+        std::unordered_map m; // expected-error{{no viable constructor or deduction guide for deduction of template arguments of 'unordered_map'}}
+    }
+    {
+        // cannot deduce Key from just (Size)
+        std::unordered_map m(42); // expected-error{{no viable constructor or deduction guide for deduction of template arguments of 'unordered_map'}}
+    }
+    {
+        // cannot deduce Key from just (Size, Hash)
+        std::unordered_map m(42, std::hash<int>());
+            // expected-error@-1{{no viable constructor or deduction guide for deduction of template arguments of 'unordered_map'}}
+    }
+    {
+        // cannot deduce Key from just (Size, Hash, Pred)
+        std::unordered_map m(42, std::hash<int>(), std::equal_to<int>());
+            // expected-error@-1{{no viable constructor or deduction guide for deduction of template arguments of 'unordered_map'}}
+    }
+    {
+        // cannot deduce Key from just (Size, Hash, Pred, Allocator)
+        std::unordered_map m(42, std::hash<int>(), std::equal_to<int>(), std::allocator<P>());
+            // expected-error@-1{{no viable constructor or deduction guide for deduction of template arguments of 'unordered_map'}}
+    }
+    {
+        // cannot deduce Key from just (Allocator)
+        std::unordered_map m(std::allocator<P>{});
+            // expected-error@-1{{no viable constructor or deduction guide for deduction of template arguments of 'unordered_map'}}
+    }
+    {
+        // cannot deduce Key from just (Size, Allocator)
+        std::unordered_map m(42, std::allocator<P>());
+            // expected-error@-1{{no viable constructor or deduction guide for deduction of template arguments of 'unordered_map'}}
+    }
+    {
+        // cannot deduce Key from just (Size, Hash, Allocator)
+        std::unordered_map m(42, std::hash<int>(), std::allocator<P>());
+            // expected-error@-1{{no viable constructor or deduction guide for deduction of template arguments of 'unordered_map'}}
+    }
+
+  return 0;
+}
Index: test/std/containers/unord/unord.map/unord.map.cnstr/deduct.pass.cpp
===================================================================
--- /dev/null
+++ test/std/containers/unord/unord.map/unord.map.cnstr/deduct.pass.cpp
@@ -0,0 +1,206 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// <unordered_map>
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+// UNSUPPORTED: libcpp-no-deduction-guides
+
+//  template<class InputIterator,
+//           class Hash = hash<iter-key-type<InputIterator>>,
+//           class Pred = equal_to<iter-key-type<InputIterator>>,
+//           class Allocator = allocator<iter-to-alloc-type<InputIterator>>>
+//  unordered_map(InputIterator, InputIterator, typename see below::size_type = see below,
+//                Hash = Hash(), Pred = Pred(), Allocator = Allocator())
+//    -> unordered_map<iter-key-type<InputIterator>, iter-mapped-type<InputIterator>, Hash, Pred,
+//                     Allocator>;
+//
+//  template<class Key, class T, class Hash = hash<Key>,
+//           class Pred = equal_to<Key>, class Allocator = allocator<pair<const Key, T>>>
+//  unordered_map(initializer_list<pair<Key, T>>,
+//                typename see below::size_type = see below, Hash = Hash(),
+//                Pred = Pred(), Allocator = Allocator())
+//    -> unordered_map<Key, T, Hash, Pred, Allocator>;
+//
+//  template<class InputIterator, class Allocator>
+//  unordered_map(InputIterator, InputIterator, typename see below::size_type, Allocator)
+//    -> unordered_map<iter-key-type<InputIterator>, iter-mapped-type<InputIterator>,
+//                     hash<iter-key-type<InputIterator>>,
+//                     equal_to<iter-key-type<InputIterator>>, Allocator>;
+//
+//  template<class InputIterator, class Allocator>
+//  unordered_map(InputIterator, InputIterator, Allocator)
+//    -> unordered_map<iter-key-type<InputIterator>, iter-mapped-type<InputIterator>,
+//                     hash<iter-key-type<InputIterator>>,
+//                     equal_to<iter-key-type<InputIterator>>, Allocator>;
+//
+//  template<class InputIterator, class Hash, class Allocator>
+//  unordered_map(InputIterator, InputIterator, typename see below::size_type, Hash, Allocator)
+//    -> unordered_map<iter-key-type<InputIterator>, iter-mapped-type<InputIterator>, Hash,
+//                     equal_to<iter-key-type<InputIterator>>, Allocator>;
+//
+//  template<class Key, class T, class Allocator>
+//  unordered_map(initializer_list<pair<Key, T>>, typename see below::size_type, Allocator)
+//    -> unordered_map<Key, T, hash<Key>, equal_to<Key>, Allocator>;
+//
+//  template<class Key, class T, class Allocator>
+//  unordered_map(initializer_list<pair<Key, T>>, Allocator)
+//    -> unordered_map<Key, T, hash<Key>, equal_to<Key>, Allocator>;
+//
+//  template<class Key, class T, class Hash, class Allocator>
+//  unordered_map(initializer_list<pair<Key, T>>, typename see below::size_type, Hash,
+//                Allocator)
+//    -> unordered_map<Key, T, Hash, equal_to<Key>, Allocator>;
+
+#include <algorithm> // is_permutation
+#include <cassert>
+#include <climits> // INT_MAX
+#include <type_traits>
+#include <unordered_map>
+
+#include "test_allocator.h"
+
+struct A {
+    friend bool operator<(A, A) { return false; }
+};
+
+int main(int, char**)
+{
+    using P = std::pair<const int, long>;
+    std::pair<const int, long> expected_m[] = { {1,1}, {2,2}, {3,1}, {INT_MAX,1} };
+
+    {
+    const std::pair<int, long> arr[] = { {1,1}, {2,2}, {1,1}, {INT_MAX,1}, {3,1} };
+    std::unordered_map m(std::begin(arr), std::end(arr));
+    ASSERT_SAME_TYPE(decltype(m), std::unordered_map<int, long>);
+    assert(std::is_permutation(m.begin(), m.end(), std::begin(expected_m), std::end(expected_m)));
+    }
+
+    {
+    const std::pair<int, long> arr[] = { {1,1}, {2,2}, {1,1}, {INT_MAX,1}, {3,1} };
+    std::unordered_map m(std::begin(arr), std::end(arr), 42);
+    ASSERT_SAME_TYPE(decltype(m), std::unordered_map<int, long>);
+    assert(std::is_permutation(m.begin(), m.end(), std::begin(expected_m), std::end(expected_m)));
+    }
+
+    {
+    const std::pair<int, long> arr[] = { {1,1}, {2,2}, {1,1}, {INT_MAX,1}, {3,1} };
+    std::unordered_map m(std::begin(arr), std::end(arr), 42, std::hash<short>());
+    ASSERT_SAME_TYPE(decltype(m), std::unordered_map<int, long, std::hash<short>, std::equal_to<int>>);
+    assert(std::is_permutation(m.begin(), m.end(), std::begin(expected_m), std::end(expected_m)));
+    }
+
+    {
+    const std::pair<int, long> arr[] = { {1,1}, {2,2}, {1,1}, {INT_MAX,1}, {3,1} };
+    std::unordered_map m(std::begin(arr), std::end(arr), 42, std::hash<short>(), std::equal_to<>());
+    ASSERT_SAME_TYPE(decltype(m), std::unordered_map<int, long, std::hash<short>, std::equal_to<>>);
+    assert(std::is_permutation(m.begin(), m.end(), std::begin(expected_m), std::end(expected_m)));
+    }
+
+    {
+    const std::pair<int, long> arr[] = { {1,1}, {2,2}, {1,1}, {INT_MAX,1}, {3,1} };
+    std::unordered_map m(std::begin(arr), std::end(arr), 42, std::hash<short>(), std::equal_to<>(), test_allocator<P>(0, 41));
+    ASSERT_SAME_TYPE(decltype(m), std::unordered_map<int, long, std::hash<short>, std::equal_to<>, test_allocator<P>>);
+    assert(std::is_permutation(m.begin(), m.end(), std::begin(expected_m), std::end(expected_m)));
+    assert(m.get_allocator().get_id() == 41);
+    }
+
+    {
+    std::unordered_map<int, long> source;
+    std::unordered_map m(source);
+    ASSERT_SAME_TYPE(decltype(m), decltype(source));
+    assert(m.size() == 0);
+    }
+
+    {
+    std::unordered_map<int, long> source;
+    std::unordered_map m{source};
+    ASSERT_SAME_TYPE(decltype(m), decltype(source));
+    assert(m.size() == 0);
+    }
+
+    {
+    std::unordered_map<int, long, std::hash<short>, std::equal_to<>, test_allocator<P>> source;
+    test_allocator<P> a(0, 42);
+    std::unordered_map m(source, a);
+    ASSERT_SAME_TYPE(decltype(m), decltype(source));
+    assert(m.get_allocator().get_id() == 42);
+    assert(m.size() == 0);
+    }
+
+    {
+    std::unordered_map<int, long, std::hash<short>, std::equal_to<>, test_allocator<P>> source;
+    test_allocator<P> a(0, 43);
+    std::unordered_map m{source, a};
+    ASSERT_SAME_TYPE(decltype(m), decltype(source));
+    assert(m.get_allocator().get_id() == 43);
+    assert(m.size() == 0);
+    }
+
+    {
+    std::unordered_map m { std::pair{1,1L}, std::pair{2,2L}, std::pair{1,1L}, std::pair{INT_MAX,1L}, std::pair{3,1L} };
+    ASSERT_SAME_TYPE(decltype(m), std::unordered_map<int, long>);
+    assert(std::is_permutation(m.begin(), m.end(), std::begin(expected_m), std::end(expected_m)));
+    }
+
+    {
+    std::unordered_map m({ std::pair{1,1L}, std::pair{2,2L}, std::pair{1,1L}, std::pair{INT_MAX,1L}, std::pair{3,1L} }, 42);
+    ASSERT_SAME_TYPE(decltype(m), std::unordered_map<int, long>);
+    assert(std::is_permutation(m.begin(), m.end(), std::begin(expected_m), std::end(expected_m)));
+    }
+
+    {
+    std::unordered_map m({ std::pair{1,1L}, std::pair{2,2L}, std::pair{1,1L}, std::pair{INT_MAX,1L}, std::pair{3,1L} }, 42, std::hash<short>());
+    ASSERT_SAME_TYPE(decltype(m), std::unordered_map<int, long, std::hash<short>>);
+    assert(std::is_permutation(m.begin(), m.end(), std::begin(expected_m), std::end(expected_m)));
+    }
+
+    {
+    std::unordered_map m({ std::pair{1,1L}, std::pair{2,2L}, std::pair{1,1L}, std::pair{INT_MAX,1L}, std::pair{3,1L} }, 42, std::hash<short>(), std::equal_to<>());
+    ASSERT_SAME_TYPE(decltype(m), std::unordered_map<int, long, std::hash<short>, std::equal_to<>>);
+    assert(std::is_permutation(m.begin(), m.end(), std::begin(expected_m), std::end(expected_m)));
+    }
+
+    {
+    std::unordered_map m({ std::pair{1,1L}, std::pair{2,2L}, std::pair{1,1L}, std::pair{INT_MAX,1L}, std::pair{3,1L} }, 42, std::hash<short>(), std::equal_to<>(), test_allocator<P>(0, 44));
+    ASSERT_SAME_TYPE(decltype(m), std::unordered_map<int, long, std::hash<short>, std::equal_to<>, test_allocator<P>>);
+    assert(std::is_permutation(m.begin(), m.end(), std::begin(expected_m), std::end(expected_m)));
+    assert(m.get_allocator().get_id() == 44);
+    }
+
+    {
+    const std::pair<int, long> arr[] = { {1,1}, {2,2}, {1,1}, {INT_MAX,1}, {3,1} };
+    std::unordered_map m(std::begin(arr), std::end(arr), 42, test_allocator<P>(0, 45));
+    ASSERT_SAME_TYPE(decltype(m), std::unordered_map<int, long, std::hash<int>, std::equal_to<int>, test_allocator<P>>);
+    assert(std::is_permutation(m.begin(), m.end(), std::begin(expected_m), std::end(expected_m)));
+    assert(m.get_allocator().get_id() == 45);
+    }
+
+    {
+    const std::pair<int, long> arr[] = { {1,1}, {2,2}, {1,1}, {INT_MAX,1}, {3,1} };
+    std::unordered_map m(std::begin(arr), std::end(arr), 42, std::hash<short>(), test_allocator<P>(0, 46));
+    ASSERT_SAME_TYPE(decltype(m), std::unordered_map<int, long, std::hash<short>, std::equal_to<int>, test_allocator<P>>);
+    assert(std::is_permutation(m.begin(), m.end(), std::begin(expected_m), std::end(expected_m)));
+    assert(m.get_allocator().get_id() == 46);
+    }
+
+    {
+    std::unordered_map m({ std::pair{1,1L}, std::pair{2,2L}, std::pair{1,1L}, std::pair{INT_MAX,1L}, std::pair{3,1L} }, 42, test_allocator<P>(0, 47));
+    ASSERT_SAME_TYPE(decltype(m), std::unordered_map<int, long, std::hash<int>, std::equal_to<int>, test_allocator<P>>);
+    assert(std::is_permutation(m.begin(), m.end(), std::begin(expected_m), std::end(expected_m)));
+    assert(m.get_allocator().get_id() == 47);
+    }
+
+    {
+    std::unordered_map m({ std::pair{1,1L}, std::pair{2,2L}, std::pair{1,1L}, std::pair{INT_MAX,1L}, std::pair{3,1L} }, 42, std::hash<short>(), test_allocator<P>(0, 48));
+    ASSERT_SAME_TYPE(decltype(m), std::unordered_map<int, long, std::hash<short>, std::equal_to<int>, test_allocator<P>>);
+    assert(std::is_permutation(m.begin(), m.end(), std::begin(expected_m), std::end(expected_m)));
+    assert(m.get_allocator().get_id() == 48);
+    }
+
+  return 0;
+}
Index: test/std/containers/unord/unord.multimap/unord.multimap.cnstr/deduct.fail.cpp
===================================================================
--- /dev/null
+++ test/std/containers/unord/unord.multimap/unord.multimap.cnstr/deduct.fail.cpp
@@ -0,0 +1,106 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// <unordered_map>
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+// UNSUPPORTED: libcpp-no-deduction-guides
+
+//  template<class InputIterator,
+//           class Hash = hash<iter-key-type<InputIterator>>,
+//           class Pred = equal_to<iter-key-type<InputIterator>>,
+//           class Allocator = allocator<iter-to-alloc-type<InputIterator>>>
+//  unordered_multimap(InputIterator, InputIterator, typename see below::size_type = see below,
+//                Hash = Hash(), Pred = Pred(), Allocator = Allocator())
+//    -> unordered_multimap<iter-key-type<InputIterator>, iter-mapped-type<InputIterator>, Hash, Pred,
+//                     Allocator>;
+//
+//  template<class Key, class T, class Hash = hash<Key>,
+//           class Pred = equal_to<Key>, class Allocator = allocator<pair<const Key, T>>>
+//  unordered_multimap(initializer_list<pair<Key, T>>,
+//                typename see below::size_type = see below, Hash = Hash(),
+//                Pred = Pred(), Allocator = Allocator())
+//    -> unordered_multimap<Key, T, Hash, Pred, Allocator>;
+//
+//  template<class InputIterator, class Allocator>
+//  unordered_multimap(InputIterator, InputIterator, typename see below::size_type, Allocator)
+//    -> unordered_multimap<iter-key-type<InputIterator>, iter-mapped-type<InputIterator>,
+//                     hash<iter-key-type<InputIterator>>,
+//                     equal_to<iter-key-type<InputIterator>>, Allocator>;
+//
+//  template<class InputIterator, class Allocator>
+//  unordered_multimap(InputIterator, InputIterator, Allocator)
+//    -> unordered_multimap<iter-key-type<InputIterator>, iter-mapped-type<InputIterator>,
+//                     hash<iter-key-type<InputIterator>>,
+//                     equal_to<iter-key-type<InputIterator>>, Allocator>;
+//
+//  template<class InputIterator, class Hash, class Allocator>
+//  unordered_multimap(InputIterator, InputIterator, typename see below::size_type, Hash, Allocator)
+//    -> unordered_multimap<iter-key-type<InputIterator>, iter-mapped-type<InputIterator>, Hash,
+//                     equal_to<iter-key-type<InputIterator>>, Allocator>;
+//
+//  template<class Key, class T, class Allocator>
+//  unordered_multimap(initializer_list<pair<Key, T>>, typename see below::size_type, Allocator)
+//    -> unordered_multimap<Key, T, hash<Key>, equal_to<Key>, Allocator>;
+//
+//  template<class Key, class T, class Allocator>
+//  unordered_multimap(initializer_list<pair<Key, T>>, Allocator)
+//    -> unordered_multimap<Key, T, hash<Key>, equal_to<Key>, Allocator>;
+//
+//  template<class Key, class T, class Hash, class Allocator>
+//  unordered_multimap(initializer_list<pair<Key, T>>, typename see below::size_type, Hash,
+//                Allocator)
+//    -> unordered_multimap<Key, T, Hash, equal_to<Key>, Allocator>;
+
+#include <climits> // INT_MAX
+#include <functional>
+#include <unordered_map>
+
+int main(int, char**)
+{
+    using P = std::pair<const int, int>;
+    {
+        // cannot deduce Key from nothing
+        std::unordered_multimap m; // expected-error{{no viable constructor or deduction guide for deduction of template arguments of 'unordered_multimap'}}
+    }
+    {
+        // cannot deduce Key from just (Size)
+        std::unordered_multimap m(42); // expected-error{{no viable constructor or deduction guide for deduction of template arguments of 'unordered_multimap'}}
+    }
+    {
+        // cannot deduce Key from just (Size, Hash)
+        std::unordered_multimap m(42, std::hash<int>());
+            // expected-error@-1{{no viable constructor or deduction guide for deduction of template arguments of 'unordered_multimap'}}
+    }
+    {
+        // cannot deduce Key from just (Size, Hash, Pred)
+        std::unordered_multimap m(42, std::hash<int>(), std::equal_to<int>());
+            // expected-error@-1{{no viable constructor or deduction guide for deduction of template arguments of 'unordered_multimap'}}
+    }
+    {
+        // cannot deduce Key from just (Size, Hash, Pred, Allocator)
+        std::unordered_multimap m(42, std::hash<int>(), std::equal_to<int>(), std::allocator<P>());
+            // expected-error@-1{{no viable constructor or deduction guide for deduction of template arguments of 'unordered_multimap'}}
+    }
+    {
+        // cannot deduce Key from just (Allocator)
+        std::unordered_multimap m(std::allocator<P>{});
+            // expected-error@-1{{no viable constructor or deduction guide for deduction of template arguments of 'unordered_multimap'}}
+    }
+    {
+        // cannot deduce Key from just (Size, Allocator)
+        std::unordered_multimap m(42, std::allocator<P>());
+            // expected-error@-1{{no viable constructor or deduction guide for deduction of template arguments of 'unordered_multimap'}}
+    }
+    {
+        // cannot deduce Key from just (Size, Hash, Allocator)
+        std::unordered_multimap m(42, std::hash<int>(), std::allocator<P>());
+            // expected-error@-1{{no viable constructor or deduction guide for deduction of template arguments of 'unordered_multimap'}}
+    }
+
+  return 0;
+}
Index: test/std/containers/unord/unord.multimap/unord.multimap.cnstr/deduct.pass.cpp
===================================================================
--- /dev/null
+++ test/std/containers/unord/unord.multimap/unord.multimap.cnstr/deduct.pass.cpp
@@ -0,0 +1,206 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// <unordered_map>
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+// UNSUPPORTED: libcpp-no-deduction-guides
+
+//  template<class InputIterator,
+//           class Hash = hash<iter-key-type<InputIterator>>,
+//           class Pred = equal_to<iter-key-type<InputIterator>>,
+//           class Allocator = allocator<iter-to-alloc-type<InputIterator>>>
+//  unordered_multimap(InputIterator, InputIterator, typename see below::size_type = see below,
+//                Hash = Hash(), Pred = Pred(), Allocator = Allocator())
+//    -> unordered_multimap<iter-key-type<InputIterator>, iter-mapped-type<InputIterator>, Hash, Pred,
+//                     Allocator>;
+//
+//  template<class Key, class T, class Hash = hash<Key>,
+//           class Pred = equal_to<Key>, class Allocator = allocator<pair<const Key, T>>>
+//  unordered_multimap(initializer_list<pair<Key, T>>,
+//                typename see below::size_type = see below, Hash = Hash(),
+//                Pred = Pred(), Allocator = Allocator())
+//    -> unordered_multimap<Key, T, Hash, Pred, Allocator>;
+//
+//  template<class InputIterator, class Allocator>
+//  unordered_multimap(InputIterator, InputIterator, typename see below::size_type, Allocator)
+//    -> unordered_multimap<iter-key-type<InputIterator>, iter-mapped-type<InputIterator>,
+//                     hash<iter-key-type<InputIterator>>,
+//                     equal_to<iter-key-type<InputIterator>>, Allocator>;
+//
+//  template<class InputIterator, class Allocator>
+//  unordered_multimap(InputIterator, InputIterator, Allocator)
+//    -> unordered_multimap<iter-key-type<InputIterator>, iter-mapped-type<InputIterator>,
+//                     hash<iter-key-type<InputIterator>>,
+//                     equal_to<iter-key-type<InputIterator>>, Allocator>;
+//
+//  template<class InputIterator, class Hash, class Allocator>
+//  unordered_multimap(InputIterator, InputIterator, typename see below::size_type, Hash, Allocator)
+//    -> unordered_multimap<iter-key-type<InputIterator>, iter-mapped-type<InputIterator>, Hash,
+//                     equal_to<iter-key-type<InputIterator>>, Allocator>;
+//
+//  template<class Key, class T, class Allocator>
+//  unordered_multimap(initializer_list<pair<Key, T>>, typename see below::size_type, Allocator)
+//    -> unordered_multimap<Key, T, hash<Key>, equal_to<Key>, Allocator>;
+//
+//  template<class Key, class T, class Allocator>
+//  unordered_multimap(initializer_list<pair<Key, T>>, Allocator)
+//    -> unordered_multimap<Key, T, hash<Key>, equal_to<Key>, Allocator>;
+//
+//  template<class Key, class T, class Hash, class Allocator>
+//  unordered_multimap(initializer_list<pair<Key, T>>, typename see below::size_type, Hash,
+//                Allocator)
+//    -> unordered_multimap<Key, T, Hash, equal_to<Key>, Allocator>;
+
+#include <algorithm> // is_permutation
+#include <cassert>
+#include <climits> // INT_MAX
+#include <type_traits>
+#include <unordered_map>
+
+#include "test_allocator.h"
+
+struct A {
+    friend bool operator<(A, A) { return false; }
+};
+
+int main(int, char**)
+{
+    using P = std::pair<const int, long>;
+    std::pair<const int, long> expected_m[] = { {1,1}, {1,1}, {2,2}, {3,1}, {INT_MAX,1} };
+
+    {
+    const std::pair<int, long> arr[] = { {1,1}, {2,2}, {1,1}, {INT_MAX,1}, {3,1} };
+    std::unordered_multimap m(std::begin(arr), std::end(arr));
+    ASSERT_SAME_TYPE(decltype(m), std::unordered_multimap<int, long>);
+    assert(std::is_permutation(m.begin(), m.end(), std::begin(expected_m), std::end(expected_m)));
+    }
+
+    {
+    const std::pair<int, long> arr[] = { {1,1}, {2,2}, {1,1}, {INT_MAX,1}, {3,1} };
+    std::unordered_multimap m(std::begin(arr), std::end(arr), 42);
+    ASSERT_SAME_TYPE(decltype(m), std::unordered_multimap<int, long>);
+    assert(std::is_permutation(m.begin(), m.end(), std::begin(expected_m), std::end(expected_m)));
+    }
+
+    {
+    const std::pair<int, long> arr[] = { {1,1}, {2,2}, {1,1}, {INT_MAX,1}, {3,1} };
+    std::unordered_multimap m(std::begin(arr), std::end(arr), 42, std::hash<short>());
+    ASSERT_SAME_TYPE(decltype(m), std::unordered_multimap<int, long, std::hash<short>, std::equal_to<int>>);
+    assert(std::is_permutation(m.begin(), m.end(), std::begin(expected_m), std::end(expected_m)));
+    }
+
+    {
+    const std::pair<int, long> arr[] = { {1,1}, {2,2}, {1,1}, {INT_MAX,1}, {3,1} };
+    std::unordered_multimap m(std::begin(arr), std::end(arr), 42, std::hash<short>(), std::equal_to<>());
+    ASSERT_SAME_TYPE(decltype(m), std::unordered_multimap<int, long, std::hash<short>, std::equal_to<>>);
+    assert(std::is_permutation(m.begin(), m.end(), std::begin(expected_m), std::end(expected_m)));
+    }
+
+    {
+    const std::pair<int, long> arr[] = { {1,1}, {2,2}, {1,1}, {INT_MAX,1}, {3,1} };
+    std::unordered_multimap m(std::begin(arr), std::end(arr), 42, std::hash<short>(), std::equal_to<>(), test_allocator<P>(0, 41));
+    ASSERT_SAME_TYPE(decltype(m), std::unordered_multimap<int, long, std::hash<short>, std::equal_to<>, test_allocator<P>>);
+    assert(std::is_permutation(m.begin(), m.end(), std::begin(expected_m), std::end(expected_m)));
+    assert(m.get_allocator().get_id() == 41);
+    }
+
+    {
+    std::unordered_multimap<int, long> source;
+    std::unordered_multimap m(source);
+    ASSERT_SAME_TYPE(decltype(m), decltype(source));
+    assert(m.size() == 0);
+    }
+
+    {
+    std::unordered_multimap<int, long> source;
+    std::unordered_multimap m{source};
+    ASSERT_SAME_TYPE(decltype(m), decltype(source));
+    assert(m.size() == 0);
+    }
+
+    {
+    std::unordered_multimap<int, long, std::hash<short>, std::equal_to<>, test_allocator<P>> source;
+    test_allocator<P> a(0, 42);
+    std::unordered_multimap m(source, a);
+    ASSERT_SAME_TYPE(decltype(m), decltype(source));
+    assert(m.get_allocator().get_id() == 42);
+    assert(m.size() == 0);
+    }
+
+    {
+    std::unordered_multimap<int, long, std::hash<short>, std::equal_to<>, test_allocator<P>> source;
+    test_allocator<P> a(0, 43);
+    std::unordered_multimap m{source, a};
+    ASSERT_SAME_TYPE(decltype(m), decltype(source));
+    assert(m.get_allocator().get_id() == 43);
+    assert(m.size() == 0);
+    }
+
+    {
+    std::unordered_multimap m { std::pair{1,1L}, std::pair{2,2L}, std::pair{1,1L}, std::pair{INT_MAX,1L}, std::pair{3,1L} };
+    ASSERT_SAME_TYPE(decltype(m), std::unordered_multimap<int, long>);
+    assert(std::is_permutation(m.begin(), m.end(), std::begin(expected_m), std::end(expected_m)));
+    }
+
+    {
+    std::unordered_multimap m({ std::pair{1,1L}, std::pair{2,2L}, std::pair{1,1L}, std::pair{INT_MAX,1L}, std::pair{3,1L} }, 42);
+    ASSERT_SAME_TYPE(decltype(m), std::unordered_multimap<int, long>);
+    assert(std::is_permutation(m.begin(), m.end(), std::begin(expected_m), std::end(expected_m)));
+    }
+
+    {
+    std::unordered_multimap m({ std::pair{1,1L}, std::pair{2,2L}, std::pair{1,1L}, std::pair{INT_MAX,1L}, std::pair{3,1L} }, 42, std::hash<short>());
+    ASSERT_SAME_TYPE(decltype(m), std::unordered_multimap<int, long, std::hash<short>>);
+    assert(std::is_permutation(m.begin(), m.end(), std::begin(expected_m), std::end(expected_m)));
+    }
+
+    {
+    std::unordered_multimap m({ std::pair{1,1L}, std::pair{2,2L}, std::pair{1,1L}, std::pair{INT_MAX,1L}, std::pair{3,1L} }, 42, std::hash<short>(), std::equal_to<>());
+    ASSERT_SAME_TYPE(decltype(m), std::unordered_multimap<int, long, std::hash<short>, std::equal_to<>>);
+    assert(std::is_permutation(m.begin(), m.end(), std::begin(expected_m), std::end(expected_m)));
+    }
+
+    {
+    std::unordered_multimap m({ std::pair{1,1L}, std::pair{2,2L}, std::pair{1,1L}, std::pair{INT_MAX,1L}, std::pair{3,1L} }, 42, std::hash<short>(), std::equal_to<>(), test_allocator<P>(0, 44));
+    ASSERT_SAME_TYPE(decltype(m), std::unordered_multimap<int, long, std::hash<short>, std::equal_to<>, test_allocator<P>>);
+    assert(std::is_permutation(m.begin(), m.end(), std::begin(expected_m), std::end(expected_m)));
+    assert(m.get_allocator().get_id() == 44);
+    }
+
+    {
+    const std::pair<int, long> arr[] = { {1,1}, {2,2}, {1,1}, {INT_MAX,1}, {3,1} };
+    std::unordered_multimap m(std::begin(arr), std::end(arr), 42, test_allocator<P>(0, 45));
+    ASSERT_SAME_TYPE(decltype(m), std::unordered_multimap<int, long, std::hash<int>, std::equal_to<int>, test_allocator<P>>);
+    assert(std::is_permutation(m.begin(), m.end(), std::begin(expected_m), std::end(expected_m)));
+    assert(m.get_allocator().get_id() == 45);
+    }
+
+    {
+    const std::pair<int, long> arr[] = { {1,1}, {2,2}, {1,1}, {INT_MAX,1}, {3,1} };
+    std::unordered_multimap m(std::begin(arr), std::end(arr), 42, std::hash<short>(), test_allocator<P>(0, 46));
+    ASSERT_SAME_TYPE(decltype(m), std::unordered_multimap<int, long, std::hash<short>, std::equal_to<int>, test_allocator<P>>);
+    assert(std::is_permutation(m.begin(), m.end(), std::begin(expected_m), std::end(expected_m)));
+    assert(m.get_allocator().get_id() == 46);
+    }
+
+    {
+    std::unordered_multimap m({ std::pair{1,1L}, std::pair{2,2L}, std::pair{1,1L}, std::pair{INT_MAX,1L}, std::pair{3,1L} }, 42, test_allocator<P>(0, 47));
+    ASSERT_SAME_TYPE(decltype(m), std::unordered_multimap<int, long, std::hash<int>, std::equal_to<int>, test_allocator<P>>);
+    assert(std::is_permutation(m.begin(), m.end(), std::begin(expected_m), std::end(expected_m)));
+    assert(m.get_allocator().get_id() == 47);
+    }
+
+    {
+    std::unordered_multimap m({ std::pair{1,1L}, std::pair{2,2L}, std::pair{1,1L}, std::pair{INT_MAX,1L}, std::pair{3,1L} }, 42, std::hash<short>(), test_allocator<P>(0, 48));
+    ASSERT_SAME_TYPE(decltype(m), std::unordered_multimap<int, long, std::hash<short>, std::equal_to<int>, test_allocator<P>>);
+    assert(std::is_permutation(m.begin(), m.end(), std::begin(expected_m), std::end(expected_m)));
+    assert(m.get_allocator().get_id() == 48);
+    }
+
+  return 0;
+}