Index: include/set
===================================================================
--- include/set
+++ include/set
@@ -836,6 +836,34 @@
 #endif
 };
 
+#ifndef _LIBCPP_HAS_NO_DEDUCTION_GUIDES
+template<class _InputIterator,
+         class _Compare = less<typename iterator_traits<_InputIterator>::value_type>,
+         class _Allocator = allocator<typename iterator_traits<_InputIterator>::value_type>,
+         class = typename enable_if<__is_allocator<_Allocator>::value, void>::type,
+         class = typename enable_if<!__is_allocator<_Compare>::value, void>::type>
+set(_InputIterator, _InputIterator, _Compare = _Compare(), _Allocator = _Allocator())
+  -> set<typename iterator_traits<_InputIterator>::value_type, _Compare, _Allocator>;
+
+template<class _Key, class _Compare = less<_Key>,
+         class _Allocator = allocator<_Key>,
+         class = typename enable_if<__is_allocator<_Allocator>::value, void>::type,
+         class = typename enable_if<!__is_allocator<_Compare>::value, void>::type>
+set(initializer_list<_Key>, _Compare = _Compare(), _Allocator = _Allocator())
+  -> set<_Key, _Compare, _Allocator>;
+
+template<class _InputIterator, class _Allocator,
+         class = typename enable_if<__is_allocator<_Allocator>::value, void>::type>
+set(_InputIterator, _InputIterator, _Allocator)
+  -> set<typename iterator_traits<_InputIterator>::value_type,
+         less<typename iterator_traits<_InputIterator>::value_type>, _Allocator>;
+
+template<class _Key, class _Allocator,
+         class = typename enable_if<__is_allocator<_Allocator>::value, void>::type>
+set(initializer_list<_Key>, _Allocator)
+  -> set<_Key, less<_Key>, _Allocator>;
+#endif
+
 #ifndef _LIBCPP_CXX03_LANG
 
 template <class _Key, class _Compare, class _Allocator>
@@ -1324,6 +1352,34 @@
 #endif
 };
 
+#ifndef _LIBCPP_HAS_NO_DEDUCTION_GUIDES
+template<class _InputIterator,
+         class _Compare = less<typename iterator_traits<_InputIterator>::value_type>,
+         class _Allocator = allocator<typename iterator_traits<_InputIterator>::value_type>,
+         class = typename enable_if<__is_allocator<_Allocator>::value, void>::type,
+         class = typename enable_if<!__is_allocator<_Compare>::value, void>::type>
+multiset(_InputIterator, _InputIterator, _Compare = _Compare(), _Allocator = _Allocator())
+  -> multiset<typename iterator_traits<_InputIterator>::value_type, _Compare, _Allocator>;
+
+template<class _Key, class _Compare = less<_Key>,
+         class _Allocator = allocator<_Key>,
+         class = typename enable_if<__is_allocator<_Allocator>::value, void>::type,
+         class = typename enable_if<!__is_allocator<_Compare>::value, void>::type>
+multiset(initializer_list<_Key>, _Compare = _Compare(), _Allocator = _Allocator())
+  -> multiset<_Key, _Compare, _Allocator>;
+
+template<class _InputIterator, class _Allocator,
+         class = typename enable_if<__is_allocator<_Allocator>::value, void>::type>
+multiset(_InputIterator, _InputIterator, _Allocator)
+  -> multiset<typename iterator_traits<_InputIterator>::value_type,
+         less<typename iterator_traits<_InputIterator>::value_type>, _Allocator>;
+
+template<class _Key, class _Allocator,
+         class = typename enable_if<__is_allocator<_Allocator>::value, void>::type>
+multiset(initializer_list<_Key>, _Allocator)
+  -> multiset<_Key, less<_Key>, _Allocator>;
+#endif
+
 #ifndef _LIBCPP_CXX03_LANG
 
 template <class _Key, class _Compare, class _Allocator>
Index: test/std/containers/associative/multiset/multiset.cons/deduct.fail.cpp
===================================================================
--- /dev/null
+++ test/std/containers/associative/multiset/multiset.cons/deduct.fail.cpp
@@ -0,0 +1,45 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// <set>
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+// UNSUPPORTED: libcpp-no-deduction-guides
+
+// template<class InputIterator,
+// class Compare = less<iter-value-type<InputIterator>>,
+// class Allocator = allocator<iter-value-type<InputIterator>>>
+//       multiset(InputIterator, InputIterator,
+//                Compare = Compare(), Allocator = Allocator())
+// -> multiset<iter-value-type<InputIterator>, Compare, Allocator>;
+//     template<class Key, class Compare = less<Key>, class Allocator = allocator<Key>>
+//       multiset(initializer_list<Key>, Compare = Compare(), Allocator = Allocator())
+//         -> multiset<Key, Compare, Allocator>;
+//     template<class InputIterator, class Allocator>
+//       multiset(InputIterator, InputIterator, Allocator)
+// -> multiset<iter-value-type<InputIterator>, less<iter-value-type<InputIterator>>, Allocator>;
+//     template<class Key, class Allocator>
+//       multiset(initializer_list<Key>, Allocator) -> multiset<Key, less<Key>, Allocator>;
+
+#include <set>
+#include <type_traits>
+
+struct A {};
+
+int main(int, char**)
+{
+    {
+        A a;
+        std::multiset s(a); // expected-error{{no viable constructor or deduction guide for deduction of template arguments of 'multiset'}}
+    }
+    {
+        std::allocator<int> a;
+        std::multiset s(a); // expected-error{{no viable constructor or deduction guide for deduction of template arguments of 'multiset'}}
+    }
+
+  return 0;
+}
Index: test/std/containers/associative/multiset/multiset.cons/deduct.pass.cpp
===================================================================
--- /dev/null
+++ test/std/containers/associative/multiset/multiset.cons/deduct.pass.cpp
@@ -0,0 +1,164 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// <set>
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+// UNSUPPORTED: libcpp-no-deduction-guides
+
+// template<class InputIterator,
+// class Compare = less<iter-value-type<InputIterator>>,
+// class Allocator = allocator<iter-value-type<InputIterator>>>
+//       multiset(InputIterator, InputIterator,
+//                Compare = Compare(), Allocator = Allocator())
+// -> multiset<iter-value-type<InputIterator>, Compare, Allocator>;
+//     template<class Key, class Compare = less<Key>, class Allocator = allocator<Key>>
+//       multiset(initializer_list<Key>, Compare = Compare(), Allocator = Allocator())
+//         -> multiset<Key, Compare, Allocator>;
+//     template<class InputIterator, class Allocator>
+//       multiset(InputIterator, InputIterator, Allocator)
+// -> multiset<iter-value-type<InputIterator>, less<iter-value-type<InputIterator>>, Allocator>;
+//     template<class Key, class Allocator>
+//       multiset(initializer_list<Key>, Allocator) -> multiset<Key, less<Key>, Allocator>;
+
+#include <set>
+#include <cassert>
+#include <climits> // INT_MAX
+
+#include "test_allocator.h"
+
+struct A {
+    friend bool operator<(A, A) { return false; }
+};
+
+int main(int, char**)
+{
+
+//  Test the explicit deduction guides
+    {
+    const int arr[] = { 1, 2, 1, INT_MAX, 3 };
+    std::multiset s(std::begin(arr), std::end(arr));
+
+    static_assert(std::is_same_v<decltype(s), std::multiset<int>>, "");
+    int expected_s[] = {1, 1, 2, 3, INT_MAX};
+    assert(std::equal(s.begin(), s.end(), std::begin(expected_s), std::end(expected_s)));
+    }
+
+    {
+    const int arr[] = { 1, 2, 1, INT_MAX, 3 };
+    std::multiset s(std::begin(arr), std::end(arr), std::greater<int>());
+
+    static_assert(std::is_same_v<decltype(s), std::multiset<int, std::greater<int>>>, "");
+    int expected_s[] = {INT_MAX, 3, 2, 1, 1};
+    assert(std::equal(s.begin(), s.end(), std::begin(expected_s), std::end(expected_s)));
+    }
+
+    {
+    const int arr[] = { 1, 2, 1, INT_MAX, 3 };
+    std::multiset s(std::begin(arr), std::end(arr), std::greater<int>(), test_allocator<int>(0, 42));
+
+    static_assert(std::is_same_v<decltype(s), std::multiset<int, std::greater<int>, test_allocator<int>>>, "");
+    int expected_s[] = {INT_MAX, 3, 2, 1, 1};
+    assert(std::equal(s.begin(), s.end(), std::begin(expected_s), std::end(expected_s)));
+    assert(s.get_allocator().get_id() == 42);
+    }
+
+    {
+    std::multiset s{ 1, 2, 1, INT_MAX, 3 };
+
+    static_assert(std::is_same_v<decltype(s), std::multiset<int>>, "");
+    int expected_s[] = {1, 1, 2, 3, INT_MAX};
+    assert(std::equal(s.begin(), s.end(), std::begin(expected_s), std::end(expected_s)));
+    }
+
+    {
+    std::multiset s({ 1, 2, 1, INT_MAX, 3 }, std::greater<int>());
+
+    static_assert(std::is_same_v<decltype(s), std::multiset<int, std::greater<int>>>, "");
+    int expected_s[] = {INT_MAX, 3, 2, 1, 1};
+    assert(std::equal(s.begin(), s.end(), std::begin(expected_s), std::end(expected_s)));
+    }
+
+    {
+    std::multiset s({ 1, 2, 1, INT_MAX, 3 }, std::greater<int>(), test_allocator<int>(0, 43));
+
+    static_assert(std::is_same_v<decltype(s), std::multiset<int, std::greater<int>, test_allocator<int>>>, "");
+    int expected_s[] = {INT_MAX, 3, 2, 1, 1};
+    assert(std::equal(s.begin(), s.end(), std::begin(expected_s), std::end(expected_s)));
+    assert(s.get_allocator().get_id() == 43);
+    }
+
+    {
+    const int arr[] = { 1, 2, 1, INT_MAX, 3 };
+    std::multiset s(std::begin(arr), std::end(arr), test_allocator<int>(0, 44));
+
+    static_assert(std::is_same_v<decltype(s), std::multiset<int, std::less<int>, test_allocator<int>>>, "");
+    int expected_s[] = {1, 1, 2, 3, INT_MAX};
+    assert(std::equal(s.begin(), s.end(), std::begin(expected_s), std::end(expected_s)));
+    assert(s.get_allocator().get_id() == 44);
+    }
+
+    {
+    std::multiset s({ 1, 2, 1, INT_MAX, 3 }, test_allocator<int>(0, 45));
+
+    static_assert(std::is_same_v<decltype(s), std::multiset<int, std::less<int>, test_allocator<int>>>, "");
+    int expected_s[] = {1, 1, 2, 3, INT_MAX};
+    assert(std::equal(s.begin(), s.end(), std::begin(expected_s), std::end(expected_s)));
+    assert(s.get_allocator().get_id() == 45);
+    }
+
+    {
+    std::multiset<long> source;
+    std::multiset s(source); // multiset(multiset &)
+    static_assert(std::is_same_v<decltype(s), std::multiset<long>>, "");
+    assert(s.size() == 0);
+    }
+
+    {
+    std::multiset<long> source;
+    std::multiset s{source}; // multiset(multiset &)
+    static_assert(std::is_same_v<decltype(s), std::multiset<long>>, "");
+    assert(s.size() == 0);
+    }
+
+    {
+    A a;
+    std::multiset s{a}; // multiset(initializer_list<A>)
+    static_assert(std::is_same_v<decltype(s), std::multiset<A>>, "");
+    assert(s.size() == 1);
+    }
+
+    {
+    std::multiset<long> source;
+    std::multiset s{source, source}; // multiset(initializer_list<multiset<long>>)
+    static_assert(std::is_same_v<decltype(s), std::multiset<std::multiset<long>>>, "");
+    assert(s.size() == 1);
+    }
+
+    {
+    A a;
+    std::multiset s{a, a}; // multiset(initializer_list<A>)
+    static_assert(std::is_same_v<decltype(s), std::multiset<A>>, "");
+    assert(s.size() == 1);
+    }
+
+    {
+    int source[3] = {3, 4, 5};
+    std::multiset s(source, source + 3); // multiset(InputIterator, InputIterator)
+    static_assert(std::is_same_v<decltype(s), std::multiset<int>>, "");
+    assert(s.size() == 3);
+    }
+
+    {
+    int source[3] = {3, 4, 5};
+    std::multiset s{source, source + 3}; // multiset(initializer_list<int*>)
+    static_assert(std::is_same_v<decltype(s), std::multiset<int*>>, "");
+    assert(s.size() == 2);
+    }
+
+  return 0;
+}
Index: test/std/containers/associative/set/set.cons/deduct.fail.cpp
===================================================================
--- /dev/null
+++ test/std/containers/associative/set/set.cons/deduct.fail.cpp
@@ -0,0 +1,45 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// <set>
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+// UNSUPPORTED: libcpp-no-deduction-guides
+
+// template<class InputIterator,
+// class Compare = less<iter-value-type<InputIterator>>,
+// class Allocator = allocator<iter-value-type<InputIterator>>>
+//       set(InputIterator, InputIterator,
+//                Compare = Compare(), Allocator = Allocator())
+// -> set<iter-value-type<InputIterator>, Compare, Allocator>;
+//     template<class Key, class Compare = less<Key>, class Allocator = allocator<Key>>
+//       set(initializer_list<Key>, Compare = Compare(), Allocator = Allocator())
+//         -> set<Key, Compare, Allocator>;
+//     template<class InputIterator, class Allocator>
+//       set(InputIterator, InputIterator, Allocator)
+// -> set<iter-value-type<InputIterator>, less<iter-value-type<InputIterator>>, Allocator>;
+//     template<class Key, class Allocator>
+//       set(initializer_list<Key>, Allocator) -> set<Key, less<Key>, Allocator>;
+
+#include <set>
+#include <type_traits>
+
+struct A {};
+
+int main(int, char**)
+{
+    {
+        A a;
+        std::set s(a); // expected-error{{no viable constructor or deduction guide for deduction of template arguments of 'set'}}
+    }
+    {
+        std::allocator<int> a;
+        std::set s(a); // expected-error{{no viable constructor or deduction guide for deduction of template arguments of 'set'}}
+    }
+
+  return 0;
+}
Index: test/std/containers/associative/set/set.cons/deduct.pass.cpp
===================================================================
--- /dev/null
+++ test/std/containers/associative/set/set.cons/deduct.pass.cpp
@@ -0,0 +1,164 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// <set>
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+// UNSUPPORTED: libcpp-no-deduction-guides
+
+// template<class InputIterator,
+// class Compare = less<iter-value-type<InputIterator>>,
+// class Allocator = allocator<iter-value-type<InputIterator>>>
+//       set(InputIterator, InputIterator,
+//                Compare = Compare(), Allocator = Allocator())
+// -> set<iter-value-type<InputIterator>, Compare, Allocator>;
+//     template<class Key, class Compare = less<Key>, class Allocator = allocator<Key>>
+//       set(initializer_list<Key>, Compare = Compare(), Allocator = Allocator())
+//         -> set<Key, Compare, Allocator>;
+//     template<class InputIterator, class Allocator>
+//       set(InputIterator, InputIterator, Allocator)
+// -> set<iter-value-type<InputIterator>, less<iter-value-type<InputIterator>>, Allocator>;
+//     template<class Key, class Allocator>
+//       set(initializer_list<Key>, Allocator) -> set<Key, less<Key>, Allocator>;
+
+#include <set>
+#include <cassert>
+#include <climits> // INT_MAX
+
+#include "test_allocator.h"
+
+struct A {
+    friend bool operator<(A, A) { return false; }
+};
+
+int main(int, char**)
+{
+
+//  Test the explicit deduction guides
+    {
+    const int arr[] = { 1, 2, 1, INT_MAX, 3 };
+    std::set s(std::begin(arr), std::end(arr));
+
+    static_assert(std::is_same_v<decltype(s), std::set<int>>, "");
+    int expected_s[] = {1, 2, 3, INT_MAX};
+    assert(std::equal(s.begin(), s.end(), std::begin(expected_s), std::end(expected_s)));
+    }
+
+    {
+    const int arr[] = { 1, 2, 1, INT_MAX, 3 };
+    std::set s(std::begin(arr), std::end(arr), std::greater<int>());
+
+    static_assert(std::is_same_v<decltype(s), std::set<int, std::greater<int>>>, "");
+    int expected_s[] = {INT_MAX, 3, 2, 1};
+    assert(std::equal(s.begin(), s.end(), std::begin(expected_s), std::end(expected_s)));
+    }
+
+    {
+    const int arr[] = { 1, 2, 1, INT_MAX, 3 };
+    std::set s(std::begin(arr), std::end(arr), std::greater<int>(), test_allocator<int>(0, 42));
+
+    static_assert(std::is_same_v<decltype(s), std::set<int, std::greater<int>, test_allocator<int>>>, "");
+    int expected_s[] = {INT_MAX, 3, 2, 1};
+    assert(std::equal(s.begin(), s.end(), std::begin(expected_s), std::end(expected_s)));
+    assert(s.get_allocator().get_id() == 42);
+    }
+
+    {
+    std::set s{ 1, 2, 1, INT_MAX, 3 };
+
+    static_assert(std::is_same_v<decltype(s), std::set<int>>, "");
+    int expected_s[] = {1, 2, 3, INT_MAX};
+    assert(std::equal(s.begin(), s.end(), std::begin(expected_s), std::end(expected_s)));
+    }
+
+    {
+    std::set s({ 1, 2, 1, INT_MAX, 3 }, std::greater<int>());
+
+    static_assert(std::is_same_v<decltype(s), std::set<int, std::greater<int>>>, "");
+    int expected_s[] = {INT_MAX, 3, 2, 1};
+    assert(std::equal(s.begin(), s.end(), std::begin(expected_s), std::end(expected_s)));
+    }
+
+    {
+    std::set s({ 1, 2, 1, INT_MAX, 3 }, std::greater<int>(), test_allocator<int>(0, 43));
+
+    static_assert(std::is_same_v<decltype(s), std::set<int, std::greater<int>, test_allocator<int>>>, "");
+    int expected_s[] = {INT_MAX, 3, 2, 1};
+    assert(std::equal(s.begin(), s.end(), std::begin(expected_s), std::end(expected_s)));
+    assert(s.get_allocator().get_id() == 43);
+    }
+
+    {
+    const int arr[] = { 1, 2, 1, INT_MAX, 3 };
+    std::set s(std::begin(arr), std::end(arr), test_allocator<int>(0, 44));
+
+    static_assert(std::is_same_v<decltype(s), std::set<int, std::less<int>, test_allocator<int>>>, "");
+    int expected_s[] = {1, 2, 3, INT_MAX};
+    assert(std::equal(s.begin(), s.end(), std::begin(expected_s), std::end(expected_s)));
+    assert(s.get_allocator().get_id() == 44);
+    }
+
+    {
+    std::set s({ 1, 2, 1, INT_MAX, 3 }, test_allocator<int>(0, 45));
+
+    static_assert(std::is_same_v<decltype(s), std::set<int, std::less<int>, test_allocator<int>>>, "");
+    int expected_s[] = {1, 2, 3, INT_MAX};
+    assert(std::equal(s.begin(), s.end(), std::begin(expected_s), std::end(expected_s)));
+    assert(s.get_allocator().get_id() == 45);
+    }
+
+    {
+    std::set<long> source;
+    std::set s(source); // set(set &)
+    static_assert(std::is_same_v<decltype(s), std::set<long>>, "");
+    assert(s.size() == 0);
+    }
+
+    {
+    std::set<long> source;
+    std::set s{source}; // set(set &)
+    static_assert(std::is_same_v<decltype(s), std::set<long>>, "");
+    assert(s.size() == 0);
+    }
+
+    {
+    A a;
+    std::set s{a}; // set(initializer_list<A>)
+    static_assert(std::is_same_v<decltype(s), std::set<A>>, "");
+    assert(s.size() == 1);
+    }
+
+    {
+    std::set<long> source;
+    std::set s{source, source}; // set(initializer_list<set<long>>)
+    static_assert(std::is_same_v<decltype(s), std::set<std::set<long>>>, "");
+    assert(s.size() == 1);
+    }
+
+    {
+    A a;
+    std::set s{a, a}; // set(initializer_list<A>)
+    static_assert(std::is_same_v<decltype(s), std::set<A>>, "");
+    assert(s.size() == 1);
+    }
+
+    {
+    int source[3] = {3, 4, 5};
+    std::set s(source, source + 3); // set(InputIterator, InputIterator)
+    static_assert(std::is_same_v<decltype(s), std::set<int>>, "");
+    assert(s.size() == 3);
+    }
+
+    {
+    int source[3] = {3, 4, 5};
+    std::set s{source, source + 3}; // set(initializer_list<int*>)
+    static_assert(std::is_same_v<decltype(s), std::set<int*>>, "");
+    assert(s.size() == 2);
+    }
+
+  return 0;
+}