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
@@ -103,10 +103,10 @@
 | `ranges::iterator_t <https://llvm.org/D100255>`_
 | `ranges::sentinel_t <https://llvm.org/D100269>`_
 | `ranges::range_difference_t <https://llvm.org/D100269>`_
-| ranges::range_size_t
+| `ranges::range_size_t <https://llvm.org/D106708>`_
 | `ranges::range_value_t <https://llvm.org/D100269>`_
 | `ranges::range_reference_t <https://llvm.org/D100269>`_
-| `ranges::range_rvalue_reference_t <https://llvm.org/D100269>`_",[range.access],Christopher Di Bella,In progress
+| `ranges::range_rvalue_reference_t <https://llvm.org/D100269>`_",[range.access],Christopher Di Bella,✅
 `[range.sized] <http://wg21.link/range.sized>`_,"| `ranges::sized_range <https://llvm.org/D102434>`_
 | `ranges::disable_sized_range <https://llvm.org/D102434>`_","| [range.primitives]
 | [range.range]",Christopher Di Bella,✅
diff --git a/libcxx/include/__ranges/concepts.h b/libcxx/include/__ranges/concepts.h
--- a/libcxx/include/__ranges/concepts.h
+++ b/libcxx/include/__ranges/concepts.h
@@ -69,6 +69,9 @@
   template <class _Tp>
   concept sized_range = range<_Tp> && requires(_Tp& __t) { ranges::size(__t); };
 
+  template<sized_range _Rp>
+  using range_size_t = decltype(ranges::size(declval<_Rp&>()));
+
   // `disable_sized_range` defined in `<__ranges/size.h>`
 
   // [range.view], views
diff --git a/libcxx/include/ranges b/libcxx/include/ranges
--- a/libcxx/include/ranges
+++ b/libcxx/include/ranges
@@ -35,14 +35,14 @@
   template<class T>
     inline constexpr bool enable_borrowed_range = false;
 
-  template<class T>
-    using iterator_t = decltype(ranges::begin(declval<T&>()));
-  template<class T>
-    using iterator_t = decltype(ranges::begin(declval<T&>()));
+  template<class R>
+    using iterator_t = decltype(ranges::begin(declval<R&>()));
   template<range R>
     using sentinel_t = decltype(ranges::end(declval<R&>()));
   template<range R>
     using range_difference_t = iter_difference_t<iterator_t<R>>;
+  template<sized_range R>
+    using range_size_t = decltype(ranges::size(declval<R&>()));
   template<range R>
     using range_value_t = iter_value_t<iterator_t<R>>;
   template<range R>
diff --git a/libcxx/test/std/ranges/range.req/range.range/range_size_t.compile.pass.cpp b/libcxx/test/std/ranges/range.req/range.range/range_size_t.compile.pass.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/std/ranges/range.req/range.range/range_size_t.compile.pass.cpp
@@ -0,0 +1,28 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+
+// template<sized_range R>
+// using range_size_t = decltype(ranges::size(declval<R&>()));
+
+#include <ranges>
+#include <concepts>
+
+#include "test_iterators.h"
+#include "test_range.h"
+
+struct Range {
+    cpp17_input_iterator<int*> begin();
+    sentinel end();
+    short size() const;
+};
+
+static_assert(std::same_as<std::ranges::range_size_t<Range>, short>);