diff --git a/libcxx/include/__algorithm/ranges_unique_copy.h b/libcxx/include/__algorithm/ranges_unique_copy.h
--- a/libcxx/include/__algorithm/ranges_unique_copy.h
+++ b/libcxx/include/__algorithm/ranges_unique_copy.h
@@ -21,7 +21,6 @@
 #include <__iterator/concepts.h>
 #include <__iterator/iterator_traits.h>
 #include <__iterator/projected.h>
-#include <__iterator/readable_traits.h>
 #include <__ranges/access.h>
 #include <__ranges/concepts.h>
 #include <__ranges/dangling.h>
diff --git a/libcxx/include/__format/format_functions.h b/libcxx/include/__format/format_functions.h
--- a/libcxx/include/__format/format_functions.h
+++ b/libcxx/include/__format/format_functions.h
@@ -36,7 +36,7 @@
 #include <__iterator/back_insert_iterator.h>
 #include <__iterator/concepts.h>
 #include <__iterator/incrementable_traits.h>
-#include <__iterator/readable_traits.h> // iter_value_t
+#include <__iterator/iterator_traits.h> // iter_value_t
 #include <__variant/monostate.h>
 #include <array>
 #include <string>
diff --git a/libcxx/include/__format/format_string.h b/libcxx/include/__format/format_string.h
--- a/libcxx/include/__format/format_string.h
+++ b/libcxx/include/__format/format_string.h
@@ -14,7 +14,7 @@
 #include <__config>
 #include <__format/format_error.h>
 #include <__iterator/concepts.h>
-#include <__iterator/readable_traits.h> // iter_value_t
+#include <__iterator/iterator_traits.h> // iter_value_t
 #include <cstddef>
 #include <cstdint>
 
diff --git a/libcxx/include/__format/formatter_output.h b/libcxx/include/__format/formatter_output.h
--- a/libcxx/include/__format/formatter_output.h
+++ b/libcxx/include/__format/formatter_output.h
@@ -28,7 +28,7 @@
 #include <__format/unicode.h>
 #include <__iterator/back_insert_iterator.h>
 #include <__iterator/concepts.h>
-#include <__iterator/readable_traits.h> // iter_value_t
+#include <__iterator/iterator_traits.h> // iter_value_t
 #include <__system_error/errc.h>
 #include <__type_traits/make_unsigned.h>
 #include <__utility/move.h>
diff --git a/libcxx/include/__format/parser_std_format_spec.h b/libcxx/include/__format/parser_std_format_spec.h
--- a/libcxx/include/__format/parser_std_format_spec.h
+++ b/libcxx/include/__format/parser_std_format_spec.h
@@ -31,7 +31,7 @@
 #include <__format/unicode.h>
 #include <__format/width_estimation_table.h>
 #include <__iterator/concepts.h>
-#include <__iterator/readable_traits.h> // iter_value_t
+#include <__iterator/iterator_traits.h> // iter_value_t
 #include <__memory/addressof.h>
 #include <__type_traits/common_type.h>
 #include <__type_traits/is_trivially_copyable.h>
diff --git a/libcxx/include/__format/unicode.h b/libcxx/include/__format/unicode.h
--- a/libcxx/include/__format/unicode.h
+++ b/libcxx/include/__format/unicode.h
@@ -16,7 +16,7 @@
 #include <__config>
 #include <__format/extended_grapheme_cluster_table.h>
 #include <__iterator/concepts.h>
-#include <__iterator/readable_traits.h> // iter_value_t
+#include <__iterator/iterator_traits.h> // iter_value_t
 #include <__type_traits/make_unsigned.h>
 #include <__utility/unreachable.h>
 #include <string_view>
diff --git a/libcxx/include/__iterator/iterator_traits.h b/libcxx/include/__iterator/iterator_traits.h
--- a/libcxx/include/__iterator/iterator_traits.h
+++ b/libcxx/include/__iterator/iterator_traits.h
@@ -534,6 +534,21 @@
 template <class _Iter>
 using __iter_reference = typename iterator_traits<_Iter>::reference;
 
+#if _LIBCPP_STD_VER >= 20
+
+// [readable.traits]
+
+// Let `RI` be `remove_cvref_t<I>`. The type `iter_value_t<I>` denotes
+// `indirectly_readable_traits<RI>::value_type` if `iterator_traits<RI>` names a specialization
+// generated from the primary template, and `iterator_traits<RI>::value_type` otherwise.
+// This has to be in this file and not readable_traits.h to break the include cycle between the two.
+template <class _Ip>
+using iter_value_t = typename conditional_t<__is_primary_template<iterator_traits<remove_cvref_t<_Ip> > >::value,
+                                            indirectly_readable_traits<remove_cvref_t<_Ip> >,
+                                            iterator_traits<remove_cvref_t<_Ip> > >::value_type;
+
+#endif // _LIBCPP_STD_VER >= 20
+
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___ITERATOR_ITERATOR_TRAITS_H
diff --git a/libcxx/include/__iterator/readable_traits.h b/libcxx/include/__iterator/readable_traits.h
--- a/libcxx/include/__iterator/readable_traits.h
+++ b/libcxx/include/__iterator/readable_traits.h
@@ -74,17 +74,6 @@
 struct indirectly_readable_traits<_Tp>
   : __cond_value_type<typename _Tp::value_type> {};
 
-template <class>
-struct iterator_traits;
-
-// Let `RI` be `remove_cvref_t<I>`. The type `iter_value_t<I>` denotes
-// `indirectly_readable_traits<RI>::value_type` if `iterator_traits<RI>` names a specialization
-// generated from the primary template, and `iterator_traits<RI>::value_type` otherwise.
-template <class _Ip>
-using iter_value_t = typename conditional_t<__is_primary_template<iterator_traits<remove_cvref_t<_Ip> > >::value,
-                                            indirectly_readable_traits<remove_cvref_t<_Ip> >,
-                                            iterator_traits<remove_cvref_t<_Ip> > >::value_type;
-
 #endif // _LIBCPP_STD_VER >= 20
 
 _LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/include/__memory/ranges_construct_at.h b/libcxx/include/__memory/ranges_construct_at.h
--- a/libcxx/include/__memory/ranges_construct_at.h
+++ b/libcxx/include/__memory/ranges_construct_at.h
@@ -13,7 +13,7 @@
 #include <__concepts/destructible.h>
 #include <__config>
 #include <__iterator/incrementable_traits.h>
-#include <__iterator/readable_traits.h>
+#include <__iterator/iterator_traits.h>
 #include <__memory/concepts.h>
 #include <__memory/construct_at.h>
 #include <__ranges/access.h>
diff --git a/libcxx/include/string_view b/libcxx/include/string_view
--- a/libcxx/include/string_view
+++ b/libcxx/include/string_view
@@ -210,7 +210,7 @@
 #include <__fwd/string_view.h>
 #include <__iterator/bounded_iter.h>
 #include <__iterator/concepts.h>
-#include <__iterator/readable_traits.h>
+#include <__iterator/iterator_traits.h>
 #include <__iterator/reverse_iterator.h>
 #include <__memory/pointer_traits.h>
 #include <__ranges/concepts.h>