diff --git a/libcxx/include/CMakeLists.txt b/libcxx/include/CMakeLists.txt
--- a/libcxx/include/CMakeLists.txt
+++ b/libcxx/include/CMakeLists.txt
@@ -26,6 +26,7 @@
   __algorithm/generate.h
   __algorithm/generate_n.h
   __algorithm/half_positive.h
+  __algorithm/in_in_result.h
   __algorithm/in_out_result.h
   __algorithm/includes.h
   __algorithm/inplace_merge.h
diff --git a/libcxx/include/__algorithm/in_in_result.h b/libcxx/include/__algorithm/in_in_result.h
new file mode 100644
--- /dev/null
+++ b/libcxx/include/__algorithm/in_in_result.h
@@ -0,0 +1,43 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___ALGORITHM_IN_IN_RESULT_H
+#define _LIBCPP___ALGORITHM_IN_IN_RESULT_H
+
+#include <__concepts/convertible_to.h>
+#include <__config>
+#include <__utility/move.h>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#ifndef _LIBCPP_HAS_NO_RANGES
+
+namespace ranges {
+template <class _I1, class _I2>
+struct in_in_result {
+  [[no_unique_address]] _I1 in1;
+  [[no_unique_address]] _I2 in2;
+
+  template <class _II1, class _II2>
+    requires convertible_to<const _I1&, _II1> && convertible_to<const _I2&, _II2>
+  constexpr operator in_in_result<_II1, _II2>() const & {
+    return {in1, in2};
+  }
+
+  template <class _II1, class _II2>
+    requires convertible_to<_I1, _II1> && convertible_to<_I2, _II2>
+    constexpr operator in_in_result<_II1, _II2>() && { return {_VSTD::move(in1), _VSTD::move(in2)}; }
+};
+} // namespace ranges
+
+#endif // _LIBCPP_HAS_NO_RANGES
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___ALGORITHM_IN_IN_RESULT_H
diff --git a/libcxx/include/algorithm b/libcxx/include/algorithm
--- a/libcxx/include/algorithm
+++ b/libcxx/include/algorithm
@@ -18,6 +18,11 @@
 namespace std
 {
 
+namespace ranges {
+  template <class I1, class I2>
+    struct in_in_result; // since C++20
+}
+
 template <class InputIterator, class Predicate>
     constexpr bool     // constexpr in C++20
     all_of(InputIterator first, InputIterator last, Predicate pred);
@@ -691,6 +696,7 @@
 #include <__algorithm/generate.h>
 #include <__algorithm/generate_n.h>
 #include <__algorithm/half_positive.h>
+#include <__algorithm/in_in_result.h>
 #include <__algorithm/in_out_result.h>
 #include <__algorithm/includes.h>
 #include <__algorithm/inplace_merge.h>
diff --git a/libcxx/include/module.modulemap b/libcxx/include/module.modulemap
--- a/libcxx/include/module.modulemap
+++ b/libcxx/include/module.modulemap
@@ -246,6 +246,7 @@
       module generate                 { private header "__algorithm/generate.h" }
       module generate_n               { private header "__algorithm/generate_n.h" }
       module half_positive            { private header "__algorithm/half_positive.h" }
+      module in_in_result             { private header "__algorithm/in_in_result.h" }
       module in_out_result            { private header "__algorithm/in_out_result.h" }
       module includes                 { private header "__algorithm/includes.h" }
       module inplace_merge            { private header "__algorithm/inplace_merge.h" }
diff --git a/libcxx/test/libcxx/diagnostics/detail.headers/algorithm/in_in_result.module.verify.cpp b/libcxx/test/libcxx/diagnostics/detail.headers/algorithm/in_in_result.module.verify.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/libcxx/diagnostics/detail.headers/algorithm/in_in_result.module.verify.cpp
@@ -0,0 +1,15 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: modules-build
+
+// WARNING: This test was generated by 'generate_private_header_tests.py'
+// and should not be edited manually.
+
+// expected-error@*:* {{use of private header from outside its module: '__algorithm/in_in_result.h'}}
+#include <__algorithm/in_in_result.h>
diff --git a/libcxx/test/std/algorithms/algorithms.results/in_in_result.pass.cpp b/libcxx/test/std/algorithms/algorithms.results/in_in_result.pass.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/std/algorithms/algorithms.results/in_in_result.pass.cpp
@@ -0,0 +1,84 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// UNSUPPORTED: libcpp-no-concepts
+// UNSUPPORTED: libcpp-has-no-incomplete-ranges
+
+// template <class I1, class I2>
+// struct in_in_result;
+
+#include <algorithm>
+#include <cassert>
+#include <type_traits>
+
+#include "MoveOnly.h"
+
+template <class T>
+struct ConstructibleFrom {
+  constexpr ConstructibleFrom(T c) : content{c} {}
+  T content;
+};
+
+struct A {
+  explicit A(int);
+};
+static_assert(!std::is_constructible_v<std::ranges::in_in_result<A, A>,
+                                       std::ranges::in_in_result<int, int>>);
+
+struct B {
+  B(const int&);
+  B(int&&);
+};
+static_assert(std::is_constructible_v<std::ranges::in_in_result<B, B>, std::ranges::in_in_result<int, int>>);
+static_assert(std::is_constructible_v<std::ranges::in_in_result<B, B>, std::ranges::in_in_result<int, int>&>);
+static_assert(std::is_constructible_v<std::ranges::in_in_result<B, B>, const std::ranges::in_in_result<int, int>>);
+static_assert(std::is_constructible_v<std::ranges::in_in_result<B, B>, const std::ranges::in_in_result<int, int>&>);
+
+struct C {
+  C(int&);
+};
+static_assert(!std::is_constructible_v<std::ranges::in_in_result<C, C>, std::ranges::in_in_result<int, int>&>);
+
+static_assert(std::is_convertible_v<         std::ranges::in_in_result<int, int>&, std::ranges::in_in_result<long, long>>);
+static_assert(!std::is_nothrow_convertible_v<std::ranges::in_in_result<int, int>&, std::ranges::in_in_result<long, long>>);
+static_assert(std::is_convertible_v<         const std::ranges::in_in_result<int, int>&, std::ranges::in_in_result<long, long>>);
+static_assert(!std::is_nothrow_convertible_v<const std::ranges::in_in_result<int, int>&, std::ranges::in_in_result<long, long>>);
+static_assert(std::is_convertible_v<         std::ranges::in_in_result<int, int>&&, std::ranges::in_in_result<long, long>>);
+static_assert(!std::is_nothrow_convertible_v<std::ranges::in_in_result<int, int>&&, std::ranges::in_in_result<long, long>>);
+static_assert(std::is_convertible_v<         const std::ranges::in_in_result<int, int>&&, std::ranges::in_in_result<long, long>>);
+static_assert(!std::is_nothrow_convertible_v<const std::ranges::in_in_result<int, int>&&, std::ranges::in_in_result<long, long>>);
+
+constexpr bool test() {
+  {
+    std::ranges::in_in_result<int, double> res{10L, 0.};
+    assert(res.in1 == 10);
+    assert(res.in2 == 0.);
+    std::ranges::in_in_result<ConstructibleFrom<int>, ConstructibleFrom<double>> res2 = res;
+    assert(res2.in1.content == 10);
+    assert(res2.in2.content == 0.);
+  }
+  {
+    std::ranges::in_in_result<MoveOnly, int> res{MoveOnly{}, 0};
+    assert(res.in1.get() == 1);
+    [[maybe_unused]] auto res2 = static_cast<std::ranges::in_in_result<MoveOnly, int>>(std::move(res));
+    assert(res.in1.get() == 0);
+  }
+  auto [in1, in2] = std::ranges::in_in_result<int, int>{1, 2};
+  assert(in1 == 1);
+  assert(in2 == 2);
+
+  return true;
+}
+
+int main(int, char**) {
+  test();
+  static_assert(test());
+
+  return 0;
+}
diff --git a/libcxx/test/std/algorithms/algorithms.results/no_unique_address.compile.pass.cpp b/libcxx/test/std/algorithms/algorithms.results/no_unique_address.compile.pass.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/std/algorithms/algorithms.results/no_unique_address.compile.pass.cpp
@@ -0,0 +1,27 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// UNSUPPORTED: libcpp-no-concepts
+// UNSUPPORTED: libcpp-has-no-incomplete-ranges
+
+// clang-cl and cl currently don't support [[no_unique_address]]
+// XFAIL: msvc
+
+// [algorithms.results]/1
+//   Each of the class templates specified in this subclause has the template parameters,
+//   data members, and special members specified below, and has no base classes or members
+//   other than those specified.
+
+#include <algorithm>
+
+struct Empty {};
+
+static_assert(sizeof(std::ranges::in_in_result<Empty, int>) == sizeof(int));
+static_assert(sizeof(std::ranges::in_in_result<int, Empty>) == sizeof(int));
+static_assert(sizeof(std::ranges::in_in_result<Empty, Empty>) == 2 * sizeof(Empty));