diff --git a/libcxx/include/CMakeLists.txt b/libcxx/include/CMakeLists.txt
index f2a85c717f843e..40ada5c9ce9efb 100644
--- a/libcxx/include/CMakeLists.txt
+++ b/libcxx/include/CMakeLists.txt
@@ -219,7 +219,6 @@ set(files
   __functional/unary_negate.h
   __functional/unwrap_ref.h
   __functional/weak_result_type.h
-  __functional_base
   __hash_table
   __ios/fpos.h
   __iterator/access.h
diff --git a/libcxx/include/__format/format_arg.h b/libcxx/include/__format/format_arg.h
index fa8a41e1723d21..df08e93d2ee334 100644
--- a/libcxx/include/__format/format_arg.h
+++ b/libcxx/include/__format/format_arg.h
@@ -15,7 +15,6 @@
 #include <__format/format_error.h>
 #include <__format/format_fwd.h>
 #include <__format/format_parse_context.h>
-#include <__functional_base>
 #include <__memory/addressof.h>
 #include <__variant/monostate.h>
 #include <string>
diff --git a/libcxx/include/__functional_base b/libcxx/include/__functional_base
deleted file mode 100644
index caa3d7fd86ce0b..00000000000000
--- a/libcxx/include/__functional_base
+++ /dev/null
@@ -1,32 +0,0 @@
-// -*- 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_FUNCTIONAL_BASE
-#define _LIBCPP_FUNCTIONAL_BASE
-
-#include <__config>
-#include <__functional/binary_function.h>
-#include <__functional/invoke.h>
-#include <__functional/operations.h>
-#include <__functional/reference_wrapper.h>
-#include <__functional/unary_function.h>
-#include <__functional/weak_result_type.h>
-#include <__memory/allocator_arg_t.h>
-#include <__memory/uses_allocator.h>
-#include <exception>
-#include <new>
-#include <type_traits>
-#include <typeinfo>
-#include <utility>
-
-#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
-#  pragma GCC system_header
-#endif
-
-#endif // _LIBCPP_FUNCTIONAL_BASE
diff --git a/libcxx/include/__memory/shared_ptr.h b/libcxx/include/__memory/shared_ptr.h
index a1a1b26be82997..0f28bcdfac11b3 100644
--- a/libcxx/include/__memory/shared_ptr.h
+++ b/libcxx/include/__memory/shared_ptr.h
@@ -15,7 +15,6 @@
 #include <__functional/binary_function.h>
 #include <__functional/operations.h>
 #include <__functional/reference_wrapper.h>
-#include <__functional_base>
 #include <__memory/addressof.h>
 #include <__memory/allocation_guard.h>
 #include <__memory/allocator.h>
diff --git a/libcxx/include/__memory/unique_ptr.h b/libcxx/include/__memory/unique_ptr.h
index 94c1704ea5f1bf..8b330508511af8 100644
--- a/libcxx/include/__memory/unique_ptr.h
+++ b/libcxx/include/__memory/unique_ptr.h
@@ -13,7 +13,6 @@
 #include <__config>
 #include <__functional/hash.h>
 #include <__functional/operations.h>
-#include <__functional_base>
 #include <__memory/allocator_traits.h> // __pointer
 #include <__memory/compressed_pair.h>
 #include <__utility/forward.h>
diff --git a/libcxx/include/bitset b/libcxx/include/bitset
index cae001a60ec521..fa37e701345bdf 100644
--- a/libcxx/include/bitset
+++ b/libcxx/include/bitset
@@ -114,7 +114,6 @@ template <size_t N> struct hash<std::bitset<N>>;
 
 #include <__bit_reference>
 #include <__config>
-#include <__functional_base>
 #include <climits>
 #include <cstddef>
 #include <iosfwd>
diff --git a/libcxx/include/experimental/__memory b/libcxx/include/experimental/__memory
index 40021691d5ae2e..749cf4c0c657fa 100644
--- a/libcxx/include/experimental/__memory
+++ b/libcxx/include/experimental/__memory
@@ -10,7 +10,6 @@
 #ifndef _LIBCPP_EXPERIMENTAL___MEMORY
 #define _LIBCPP_EXPERIMENTAL___MEMORY
 
-#include <__functional_base>
 #include <__memory/allocator_arg_t.h>
 #include <__memory/uses_allocator.h>
 #include <experimental/__config>
diff --git a/libcxx/include/iterator b/libcxx/include/iterator
index da920f3d1c0e63..202667809dcafb 100644
--- a/libcxx/include/iterator
+++ b/libcxx/include/iterator
@@ -598,7 +598,6 @@ template <class E> constexpr const E* data(initializer_list<E> il) noexcept;
 
 #include <__config>
 #include <__debug>
-#include <__functional_base>
 #include <__iterator/access.h>
 #include <__iterator/advance.h>
 #include <__iterator/back_insert_iterator.h>
@@ -643,6 +642,19 @@ template <class E> constexpr const E* data(initializer_list<E> il) noexcept;
 #include <utility>
 #include <version>
 
+// TODO: remove these headers
+#include <__functional/binary_function.h>
+#include <__functional/invoke.h>
+#include <__functional/operations.h>
+#include <__functional/reference_wrapper.h>
+#include <__functional/unary_function.h>
+#include <__functional/weak_result_type.h>
+#include <__memory/allocator_arg_t.h>
+#include <__memory/uses_allocator.h>
+#include <exception>
+#include <new>
+#include <typeinfo>
+
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
diff --git a/libcxx/include/memory b/libcxx/include/memory
index 0d3f5a5555738f..3bc31d29ed6c54 100644
--- a/libcxx/include/memory
+++ b/libcxx/include/memory
@@ -805,7 +805,6 @@ void* align(size_t alignment, size_t size, void*& ptr, size_t& space);
 */
 
 #include <__config>
-#include <__functional_base>
 #include <__memory/addressof.h>
 #include <__memory/allocation_guard.h>
 #include <__memory/allocator.h>
@@ -837,6 +836,14 @@ void* align(size_t alignment, size_t size, void*& ptr, size_t& space);
 #include <utility>
 #include <version>
 
+// TODO: remove these headers
+#include <__functional/binary_function.h>
+#include <__functional/invoke.h>
+#include <__functional/operations.h>
+#include <__functional/reference_wrapper.h>
+#include <__functional/unary_function.h>
+#include <__functional/weak_result_type.h>
+
 #if _LIBCPP_STD_VER <= 14 || defined(_LIBCPP_ENABLE_CXX17_REMOVED_AUTO_PTR)
 #   include <__memory/auto_ptr.h>
 #endif
diff --git a/libcxx/include/optional b/libcxx/include/optional
index 236842d627d938..1599efdd32069e 100644
--- a/libcxx/include/optional
+++ b/libcxx/include/optional
@@ -162,7 +162,6 @@ template<class T>
 #include <__concepts/invocable.h>
 #include <__config>
 #include <__debug>
-#include <__functional_base>
 #include <compare>
 #include <functional>
 #include <initializer_list>
@@ -172,6 +171,11 @@ template<class T>
 #include <utility>
 #include <version>
 
+// TODO: remove these headers
+#include <__memory/allocator_arg_t.h>
+#include <__memory/uses_allocator.h>
+#include <typeinfo>
+
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
diff --git a/libcxx/include/string b/libcxx/include/string
index 4f3815f53e7b1e..fa42edde0aa150 100644
--- a/libcxx/include/string
+++ b/libcxx/include/string
@@ -520,7 +520,6 @@ basic_string<char32_t> operator "" s( const char32_t *str, size_t len ); // C++1
 
 #include <__config>
 #include <__debug>
-#include <__functional_base>
 #include <__ios/fpos.h>
 #include <__iterator/wrap_iter.h>
 #include <algorithm>
@@ -538,6 +537,16 @@ basic_string<char32_t> operator "" s( const char32_t *str, size_t len ); // C++1
 #include <utility>
 #include <version>
 
+// TODO: remove these headers
+#include <__functional/binary_function.h>
+#include <__functional/invoke.h>
+#include <__functional/operations.h>
+#include <__functional/reference_wrapper.h>
+#include <__functional/unary_function.h>
+#include <__functional/weak_result_type.h>
+#include <new>
+#include <typeinfo>
+
 #ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
 #  include <cwchar>
 #endif
diff --git a/libcxx/include/system_error b/libcxx/include/system_error
index 78dddc93059e86..66a3f3c1e0b7ff 100644
--- a/libcxx/include/system_error
+++ b/libcxx/include/system_error
@@ -145,7 +145,6 @@ template <> struct hash<std::error_condition>;
 #include <__config>
 #include <__errc>
 #include <__functional/unary_function.h>
-#include <__functional_base>
 #include <compare>
 #include <stdexcept>
 #include <string>
diff --git a/libcxx/include/thread b/libcxx/include/thread
index 8af1e0f994735a..5681f9d97386ee 100644
--- a/libcxx/include/thread
+++ b/libcxx/include/thread
@@ -84,7 +84,6 @@ void sleep_for(const chrono::duration<Rep, Period>& rel_time);
 
 #include <__config>
 #include <__debug>
-#include <__functional_base>
 #include <__mutex_base>
 #include <__thread/poll_with_backoff.h>
 #include <__thread/timed_backoff_policy.h>
diff --git a/libcxx/include/tuple b/libcxx/include/tuple
index 046a242befdc4a..a28a2e81db3ecf 100644
--- a/libcxx/include/tuple
+++ b/libcxx/include/tuple
@@ -169,7 +169,6 @@ template <class... Types>
 #include <__compare/synth_three_way.h>
 #include <__config>
 #include <__functional/unwrap_ref.h>
-#include <__functional_base>
 #include <__memory/allocator_arg_t.h>
 #include <__memory/uses_allocator.h>
 #include <__tuple>
@@ -182,6 +181,17 @@ template <class... Types>
 #include <utility>
 #include <version>
 
+// TODO: remove these headers
+#include <__functional/binary_function.h>
+#include <__functional/invoke.h>
+#include <__functional/operations.h>
+#include <__functional/reference_wrapper.h>
+#include <__functional/unary_function.h>
+#include <__functional/weak_result_type.h>
+#include <exception>
+#include <new>
+#include <typeinfo>
+
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
diff --git a/libcxx/include/typeindex b/libcxx/include/typeindex
index c018b3c9f87499..b5dcd8496ae029 100644
--- a/libcxx/include/typeindex
+++ b/libcxx/include/typeindex
@@ -46,11 +46,21 @@ struct hash<type_index>
 
 #include <__config>
 #include <__functional/unary_function.h>
-#include <__functional_base>
 #include <compare>
 #include <typeinfo>
 #include <version>
 
+// TODO: remove these headers
+#include <__functional/binary_function.h>
+#include <__functional/invoke.h>
+#include <__functional/operations.h>
+#include <__functional/reference_wrapper.h>
+#include <__functional/weak_result_type.h>
+#include <__memory/allocator_arg_t.h>
+#include <__memory/uses_allocator.h>
+#include <new>
+#include <utility>
+
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
diff --git a/libcxx/include/variant b/libcxx/include/variant
index 38daf672c41de4..d102196f60a219 100644
--- a/libcxx/include/variant
+++ b/libcxx/include/variant
@@ -202,6 +202,8 @@ namespace std {
 #include <__availability>
 #include <__config>
 #include <__functional/hash.h>
+#include <__functional/operations.h>
+#include <__functional/unary_function.h>
 #include <__tuple>
 #include <__utility/forward.h>
 #include <__variant/monostate.h>
@@ -215,6 +217,15 @@ namespace std {
 #include <utility>
 #include <version>
 
+// TODO: remove these headers
+#include <__functional/binary_function.h>
+#include <__functional/invoke.h>
+#include <__functional/reference_wrapper.h>
+#include <__functional/weak_result_type.h>
+#include <__memory/allocator_arg_t.h>
+#include <__memory/uses_allocator.h>
+#include <typeinfo>
+
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
diff --git a/libcxx/include/vector b/libcxx/include/vector
index f92caf941e8d8c..43584e0675e351 100644
--- a/libcxx/include/vector
+++ b/libcxx/include/vector
@@ -274,7 +274,6 @@ erase_if(vector<T, Allocator>& c, Predicate pred);    // C++20
 #include <__bit_reference>
 #include <__config>
 #include <__debug>
-#include <__functional_base>
 #include <__iterator/iterator_traits.h>
 #include <__iterator/wrap_iter.h>
 #include <__split_buffer>
@@ -292,6 +291,16 @@ erase_if(vector<T, Allocator>& c, Predicate pred);    // C++20
 #include <type_traits>
 #include <version>
 
+// TODO: remove these headers
+#include <__functional/binary_function.h>
+#include <__functional/invoke.h>
+#include <__functional/operations.h>
+#include <__functional/reference_wrapper.h>
+#include <__functional/unary_function.h>
+#include <__functional/weak_result_type.h>
+#include <typeinfo>
+#include <utility>
+
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
diff --git a/libcxx/test/std/ranges/range.factories/range.iota.view/iterator/member_typedefs.compile.pass.cpp b/libcxx/test/std/ranges/range.factories/range.iota.view/iterator/member_typedefs.compile.pass.cpp
index 26d6bafbe5eedc..4dcf5d18ebbc2c 100644
--- a/libcxx/test/std/ranges/range.factories/range.iota.view/iterator/member_typedefs.compile.pass.cpp
+++ b/libcxx/test/std/ranges/range.factories/range.iota.view/iterator/member_typedefs.compile.pass.cpp
@@ -12,8 +12,9 @@
 
 // Test iterator category and iterator concepts.
 
-#include <ranges>
 #include <cassert>
+#include <cstdint>
+#include <ranges>
 
 #include "test_macros.h"
 #include "../types.h"
diff --git a/libcxx/test/std/ranges/range.factories/range.iota.view/iterator/minus.pass.cpp b/libcxx/test/std/ranges/range.factories/range.iota.view/iterator/minus.pass.cpp
index f4181801a948ff..01c8539ec90475 100644
--- a/libcxx/test/std/ranges/range.factories/range.iota.view/iterator/minus.pass.cpp
+++ b/libcxx/test/std/ranges/range.factories/range.iota.view/iterator/minus.pass.cpp
@@ -15,8 +15,9 @@
 // friend constexpr difference_type operator-(const iterator& x, const iterator& y)
 //   requires advanceable<W>;
 
-#include <ranges>
 #include <cassert>
+#include <cstdint>
+#include <ranges>
 
 #include "test_macros.h"
 #include "../types.h"
diff --git a/libcxx/utils/generate_private_header_tests.py b/libcxx/utils/generate_private_header_tests.py
index 81051a9f5ea781..e6eecd68ae506a 100755
--- a/libcxx/utils/generate_private_header_tests.py
+++ b/libcxx/utils/generate_private_header_tests.py
@@ -53,7 +53,7 @@ def is_still_public(path):
     rp = relative_path(path)
     return not rp.startswith('__support') and rp not in [
         "__bsd_locale_defaults.h", "__bsd_locale_fallbacks.h", "__config",
-        "__config_site.in", "__debug", "__hash_table", "__functional_base",
+        "__config_site.in", "__debug", "__hash_table",
         "__libcpp_version", "__threading_support", "__tree", "__undef_macros"
     ]
 
diff --git a/llvm/utils/gn/secondary/libcxx/include/BUILD.gn b/llvm/utils/gn/secondary/libcxx/include/BUILD.gn
index f06735b4593312..164923f0014bf2 100644
--- a/llvm/utils/gn/secondary/libcxx/include/BUILD.gn
+++ b/llvm/utils/gn/secondary/libcxx/include/BUILD.gn
@@ -274,7 +274,6 @@ if (current_toolchain == default_toolchain) {
       "__functional/unary_negate.h",
       "__functional/unwrap_ref.h",
       "__functional/weak_result_type.h",
-      "__functional_base",
       "__hash_table",
       "__ios/fpos.h",
       "__iterator/access.h",