diff --git a/libcxx/docs/Status/RangesPaper.csv b/libcxx/docs/Status/RangesPaper.csv
--- a/libcxx/docs/Status/RangesPaper.csv
+++ b/libcxx/docs/Status/RangesPaper.csv
@@ -133,7 +133,7 @@
 `[range.dangling] <http://wg21.link/range.dangling>`_,"| ranges::dangling
 | ranges::borrowed_iterator_t
 | ranges::borrowed_subrange_t","| [range.range]
-| [range.subrange]",Unassigned,Not started
+| [range.subrange]",Christopher Di Bella,✅
 `[range.all] <http://wg21.link/range.all>`_,`view::all <https://llvm.org/D102028>`_,"[range.subrange], [range.view.ref]",Zoe Carver,In progress
 `[range.view.ref] <http://wg21.link/range.view>`_,`ref-view <https://llvm.org/D102020>`_,[view.interface],Zoe Carver,In progress
 `[range.filter] <http://wg21.link/range.filter>`_,filter_view,[range.all],Louis Dionne,Not started
diff --git a/libcxx/include/CMakeLists.txt b/libcxx/include/CMakeLists.txt
--- a/libcxx/include/CMakeLists.txt
+++ b/libcxx/include/CMakeLists.txt
@@ -185,6 +185,7 @@
   __ranges/all.h
   __ranges/concepts.h
   __ranges/copyable_box.h
+  __ranges/dangling.h
   __ranges/data.h
   __ranges/drop_view.h
   __ranges/empty_view.h
diff --git a/libcxx/include/__ranges/dangling.h b/libcxx/include/__ranges/dangling.h
new file mode 100644
--- /dev/null
+++ b/libcxx/include/__ranges/dangling.h
@@ -0,0 +1,47 @@
+// -*- 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___RANGES_DANGLING_H
+#define _LIBCPP___RANGES_DANGLING_H
+
+#include <__config>
+#include <__ranges/access.h>
+#include <__ranges/concepts.h>
+#include <type_traits>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if !defined(_LIBCPP_HAS_NO_RANGES)
+
+namespace ranges {
+struct dangling {
+  dangling() = default;
+  _LIBCPP_HIDE_FROM_ABI constexpr dangling(auto&&...) noexcept {}
+};
+
+template <range _Rp>
+using borrowed_iterator_t = _If<borrowed_range<_Rp>, iterator_t<_Rp>, dangling>;
+
+// borrowed_subrange_t defined in <__ranges/subrange.h>
+} // namespace ranges
+
+#endif // !_LIBCPP_HAS_NO_RANGES
+
+_LIBCPP_END_NAMESPACE_STD
+
+_LIBCPP_POP_MACROS
+
+#endif // _LIBCPP___RANGES_DANGLING_H
diff --git a/libcxx/include/__ranges/subrange.h b/libcxx/include/__ranges/subrange.h
--- a/libcxx/include/__ranges/subrange.h
+++ b/libcxx/include/__ranges/subrange.h
@@ -16,6 +16,7 @@
 #include <__iterator/advance.h>
 #include <__ranges/access.h>
 #include <__ranges/concepts.h>
+#include <__ranges/dangling.h>
 #include <__ranges/enable_borrowed_range.h>
 #include <__ranges/size.h>
 #include <__ranges/view_interface.h>
@@ -226,6 +227,9 @@
     else
       return __subrange.end();
   }
+
+  template<range _Rp>
+  using borrowed_subrange_t = _If<borrowed_range<_Rp>, subrange<iterator_t<_Rp> >, dangling>;
 } // namespace ranges
 
 using ranges::get;
diff --git a/libcxx/include/module.modulemap b/libcxx/include/module.modulemap
--- a/libcxx/include/module.modulemap
+++ b/libcxx/include/module.modulemap
@@ -601,6 +601,7 @@
       module all                    { header "__ranges/all.h"                   }
       module concepts               { header "__ranges/concepts.h"              }
       module copyable_box           { header "__ranges/copyable_box.h"          }
+      module dangling               { header "__ranges/dangling.h"              }
       module data                   { header "__ranges/data.h"                  }
       module empty                  { header "__ranges/empty.h"                 }
       module empty_view             { header "__ranges/empty_view.h"            }
diff --git a/libcxx/include/ranges b/libcxx/include/ranges
--- a/libcxx/include/ranges
+++ b/libcxx/include/ranges
@@ -90,6 +90,25 @@
     requires is_class_v<D> && same_as<D, remove_cv_t<D>>
   class view_interface;
 
+  // [range.subrange], sub-ranges
+  enum class subrange_kind : bool { unsized, sized };
+
+  template<input_or_output_iterator I, sentinel_for<I> S = I, subrange_kind K = see below>
+    requires (K == subrange_kind::sized || !sized_sentinel_for<S, I>)
+  class subrange;
+
+  template<class I, class S, subrange_kind K>
+    inline constexpr bool enable_borrowed_range<subrange<I, S, K>> = true;
+
+  // [range.dangling], dangling iterator handling
+  struct dangling;
+
+  template<range R>
+    using borrowed_iterator_t = see below;
+
+  template<range R>
+    using borrowed_subrange_t = see below;
+
   // [range.empty], empty view
   template<class T>
     requires is_object_v<T>
@@ -109,6 +128,7 @@
 #include <__ranges/access.h>
 #include <__ranges/all.h>
 #include <__ranges/concepts.h>
+#include <__ranges/dangling.h>
 #include <__ranges/data.h>
 #include <__ranges/drop_view.h>
 #include <__ranges/empty.h>
diff --git a/libcxx/test/std/ranges/range.utility/range.dangling/borrowed_iterator.compile.pass.cpp b/libcxx/test/std/ranges/range.utility/range.dangling/borrowed_iterator.compile.pass.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/std/ranges/range.utility/range.dangling/borrowed_iterator.compile.pass.cpp
@@ -0,0 +1,42 @@
+//===----------------------------------------------------------------------===//
+//
+// 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: gcc-10
+
+// class std::ranges::borrowed_iterator_t;
+
+#include <ranges>
+
+#include <concepts>
+#include <span>
+#include <string>
+#include <string_view>
+#include <vector>
+
+static_assert(std::same_as<std::ranges::borrowed_iterator_t<std::string>, std::ranges::dangling>);
+static_assert(std::same_as<std::ranges::borrowed_iterator_t<std::string&&>, std::ranges::dangling>);
+static_assert(std::same_as<std::ranges::borrowed_iterator_t<std::vector<int> >, std::ranges::dangling>);
+
+static_assert(std::same_as<std::ranges::borrowed_iterator_t<std::string&>, std::string::iterator>);
+static_assert(std::same_as<std::ranges::borrowed_iterator_t<std::string_view>, std::string_view::iterator>);
+static_assert(std::same_as<std::ranges::borrowed_iterator_t<std::span<int> >, std::span<int>::iterator>);
+
+template <class T>
+constexpr bool has_borrowed_iterator = requires {
+  typename std::ranges::borrowed_iterator_t<T>;
+};
+
+static_assert(!has_borrowed_iterator<int>);
+
+template<int> struct S { };
+static_assert(std::is_nothrow_constructible_v<std::ranges::dangling>);
+static_assert(std::is_nothrow_constructible_v<std::ranges::dangling, S<0>>);
+static_assert(std::is_nothrow_constructible_v<std::ranges::dangling, S<0>, S<1>>);
+static_assert(std::is_nothrow_constructible_v<std::ranges::dangling, S<0>, S<1>, S<2>>);
diff --git a/libcxx/test/std/ranges/range.utility/range.dangling/borrowed_subrange.compile.pass.cpp b/libcxx/test/std/ranges/range.utility/range.dangling/borrowed_subrange.compile.pass.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/std/ranges/range.utility/range.dangling/borrowed_subrange.compile.pass.cpp
@@ -0,0 +1,44 @@
+//===----------------------------------------------------------------------===//
+//
+// 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: gcc-10
+
+// class std::ranges::borrowed_subrange_t;
+
+#include <ranges>
+
+#include <concepts>
+#include <span>
+#include <string>
+#include <string_view>
+#include <vector>
+
+static_assert(std::same_as<std::ranges::borrowed_subrange_t<std::string>, std::ranges::dangling>);
+static_assert(std::same_as<std::ranges::borrowed_subrange_t<std::string&&>, std::ranges::dangling>);
+static_assert(std::same_as<std::ranges::borrowed_subrange_t<std::vector<int> >, std::ranges::dangling>);
+
+static_assert(
+    std::same_as<std::ranges::borrowed_subrange_t<std::string&>, std::ranges::subrange<std::string::iterator> >);
+
+static_assert(
+    std::same_as<std::ranges::borrowed_subrange_t<std::span<int> >, std::ranges::subrange<std::span<int>::iterator> >);
+
+static_assert(std::same_as<std::ranges::borrowed_subrange_t<std::string_view>,
+                           std::ranges::subrange<std::string_view::iterator> >);
+
+template <class T>
+constexpr bool has_type = requires {
+  typename std::ranges::borrowed_subrange_t<T>;
+};
+
+static_assert(!has_type<int>);
+
+struct S {};
+static_assert(!has_type<S>);
diff --git a/libcxx/test/std/ranges/range.utility/range.dangling/dangling.compile.pass.cpp b/libcxx/test/std/ranges/range.utility/range.dangling/dangling.compile.pass.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/std/ranges/range.utility/range.dangling/dangling.compile.pass.cpp
@@ -0,0 +1,30 @@
+//===----------------------------------------------------------------------===//
+//
+// 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: gcc-10
+
+// class std::ranges::dangling;
+
+#include <ranges>
+
+#include <concepts>
+#include <type_traits>
+
+static_assert(std::default_initializable<std::ranges::dangling>);
+
+static_assert(std::is_nothrow_constructible_v<std::ranges::dangling, int>);
+static_assert(std::is_nothrow_constructible_v<std::ranges::dangling, int*>);
+static_assert(std::is_nothrow_constructible_v<std::ranges::dangling, int (*)()>);
+static_assert(std::is_nothrow_constructible_v<std::ranges::dangling, int, int, int>);
+
+struct S {};
+static_assert(std::is_nothrow_constructible_v<std::ranges::dangling, S>);
+
+static_assert(std::is_empty_v<std::ranges::dangling>);