diff --git a/libcxx/include/__ranges/join_view.h b/libcxx/include/__ranges/join_view.h
--- a/libcxx/include/__ranges/join_view.h
+++ b/libcxx/include/__ranges/join_view.h
@@ -9,8 +9,15 @@
 #ifndef _LIBCPP___RANGES_JOIN_VIEW_H
 #define _LIBCPP___RANGES_JOIN_VIEW_H
 
+#include <__concepts/constructible.h>
+#include <__concepts/convertible_to.h>
+#include <__concepts/copyable.h>
+#include <__concepts/derived_from.h>
+#include <__concepts/equality_comparable.h>
 #include <__config>
 #include <__iterator/concepts.h>
+#include <__iterator/iter_move.h>
+#include <__iterator/iter_swap.h>
 #include <__iterator/iterator_traits.h>
 #include <__ranges/access.h>
 #include <__ranges/all.h>
diff --git a/libcxx/include/algorithm b/libcxx/include/algorithm
--- a/libcxx/include/algorithm
+++ b/libcxx/include/algorithm
@@ -881,7 +881,7 @@
 #include <__debug>
 #include <cstddef>
 #include <cstring>
-#include <functional>
+#include <functional> // TODO: Remove this include
 #include <initializer_list>
 #include <iterator>
 #include <memory>
diff --git a/libcxx/include/experimental/coroutine b/libcxx/include/experimental/coroutine
--- a/libcxx/include/experimental/coroutine
+++ b/libcxx/include/experimental/coroutine
@@ -46,9 +46,10 @@
  */
 
 #include <__assert> // all public C++ headers provide the assertion handler
+#include <__functional/hash.h>
 #include <cstddef>
 #include <experimental/__config>
-#include <functional>
+#include <functional> // TODO: Remove this include
 #include <memory> // for hash<T*>
 #include <new>
 #include <type_traits>
diff --git a/libcxx/include/experimental/propagate_const b/libcxx/include/experimental/propagate_const
--- a/libcxx/include/experimental/propagate_const
+++ b/libcxx/include/experimental/propagate_const
@@ -108,10 +108,12 @@
 */
 
 #include <__assert> // all public C++ headers provide the assertion handler
+#include <__functional/operations.h>
+#include <__utility/forward.h>
 #include <__utility/move.h>
 #include <__utility/swap.h>
 #include <experimental/__config>
-#include <functional>
+#include <functional> // TODO: Remove this include
 #include <type_traits>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
diff --git a/libcxx/include/experimental/simd b/libcxx/include/experimental/simd
--- a/libcxx/include/experimental/simd
+++ b/libcxx/include/experimental/simd
@@ -650,10 +650,12 @@
 */
 
 #include <__assert> // all public C++ headers provide the assertion handler
+#include <__functional/operations.h>
 #include <array>
 #include <cstddef>
 #include <experimental/__config>
-#include <functional>
+#include <functional> // TODO: Remove this include
+#include <tuple>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
diff --git a/libcxx/include/ext/hash_map b/libcxx/include/ext/hash_map
--- a/libcxx/include/ext/hash_map
+++ b/libcxx/include/ext/hash_map
@@ -206,7 +206,7 @@
 #include <__hash_table>
 #include <algorithm>
 #include <ext/__hash>
-#include <functional>
+#include <functional> // TODO: Remove this include
 #include <stdexcept>
 #include <type_traits>
 
diff --git a/libcxx/include/ext/hash_set b/libcxx/include/ext/hash_set
--- a/libcxx/include/ext/hash_set
+++ b/libcxx/include/ext/hash_set
@@ -197,7 +197,7 @@
 #include <__hash_table>
 #include <algorithm>
 #include <ext/__hash>
-#include <functional>
+#include <functional> // TODO: Remove this include
 
 #if defined(__DEPRECATED) && __DEPRECATED
 #if defined(_LIBCPP_WARNING)
diff --git a/libcxx/include/map b/libcxx/include/map
--- a/libcxx/include/map
+++ b/libcxx/include/map
@@ -539,7 +539,7 @@
 #include <__utility/forward.h>
 #include <__utility/swap.h>
 #include <compare>
-#include <functional>
+#include <functional> // TODO: Remove this include
 #include <initializer_list>
 #include <iterator> // __libcpp_erase_if_container
 #include <memory>
diff --git a/libcxx/include/mutex b/libcxx/include/mutex
--- a/libcxx/include/mutex
+++ b/libcxx/include/mutex
@@ -192,7 +192,7 @@
 #include <__threading_support>
 #include <__utility/forward.h>
 #include <cstdint>
-#include <functional>
+#include <functional> // TODO: Remove this include
 #include <memory>
 #ifndef _LIBCPP_CXX03_LANG
 # include <tuple>
diff --git a/libcxx/include/numeric b/libcxx/include/numeric
--- a/libcxx/include/numeric
+++ b/libcxx/include/numeric
@@ -147,7 +147,7 @@
 #include <__assert> // all public C++ headers provide the assertion handler
 #include <__config>
 #include <cmath> // for isnormal
-#include <functional>
+#include <functional> // TODO: Remove this include
 #include <iterator>
 #include <version>
 
diff --git a/libcxx/include/optional b/libcxx/include/optional
--- a/libcxx/include/optional
+++ b/libcxx/include/optional
@@ -162,10 +162,17 @@
 #include <__availability>
 #include <__concepts/invocable.h>
 #include <__config>
+#include <__functional/hash.h>
+#include <__functional/invoke.h>
+#include <__functional/unary_function.h>
+#include <__memory/construct_at.h>
+#include <__tuple>
+#include <__utility/forward.h>
 #include <__utility/in_place.h>
+#include <__utility/move.h>
 #include <__utility/swap.h>
 #include <compare>
-#include <functional>
+#include <functional> // TODO: Remove this include
 #include <initializer_list>
 #include <new>
 #include <stdexcept>
diff --git a/libcxx/include/queue b/libcxx/include/queue
--- a/libcxx/include/queue
+++ b/libcxx/include/queue
@@ -227,7 +227,7 @@
 #include <__utility/forward.h>
 #include <compare>
 #include <deque>
-#include <functional>
+#include <functional> // TODO: Remove this include
 #include <type_traits>
 #include <vector>
 #include <version>
diff --git a/libcxx/include/regex b/libcxx/include/regex
--- a/libcxx/include/regex
+++ b/libcxx/include/regex
@@ -763,6 +763,7 @@
 */
 
 #include <__algorithm/find.h>
+#include <__algorithm/search.h>
 #include <__assert> // all public C++ headers provide the assertion handler
 #include <__config>
 #include <__iterator/wrap_iter.h>
diff --git a/libcxx/include/set b/libcxx/include/set
--- a/libcxx/include/set
+++ b/libcxx/include/set
@@ -481,7 +481,7 @@
 #include <__tree>
 #include <__utility/forward.h>
 #include <compare>
-#include <functional>
+#include <functional> // TODO: Remove this include
 #include <initializer_list>
 #include <iterator> // __libcpp_erase_if_container
 #include <version>
diff --git a/libcxx/include/thread b/libcxx/include/thread
--- a/libcxx/include/thread
+++ b/libcxx/include/thread
@@ -90,7 +90,7 @@
 #include <__threading_support>
 #include <__utility/forward.h>
 #include <cstddef>
-#include <functional>
+#include <functional> // TODO: Remove this include
 #include <iosfwd>
 #include <memory>
 #include <system_error>
diff --git a/libcxx/include/unordered_map b/libcxx/include/unordered_map
--- a/libcxx/include/unordered_map
+++ b/libcxx/include/unordered_map
@@ -525,7 +525,7 @@
 #include <__node_handle>
 #include <__utility/forward.h>
 #include <compare>
-#include <functional>
+#include <functional> // TODO: Remove this include
 #include <iterator> // __libcpp_erase_if_container
 #include <stdexcept>
 #include <tuple>
diff --git a/libcxx/include/unordered_set b/libcxx/include/unordered_set
--- a/libcxx/include/unordered_set
+++ b/libcxx/include/unordered_set
@@ -469,7 +469,7 @@
 #include <__node_handle>
 #include <__utility/forward.h>
 #include <compare>
-#include <functional>
+#include <functional> // TODO: Remove this include
 #include <iterator> // __libcpp_erase_if_container
 #include <version>
 
diff --git a/libcxx/include/valarray b/libcxx/include/valarray
--- a/libcxx/include/valarray
+++ b/libcxx/include/valarray
@@ -350,9 +350,14 @@
 #include <__algorithm/unwrap_iter.h>
 #include <__assert> // all public C++ headers provide the assertion handler
 #include <__config>
+#include <__functional/operations.h>
+#include <__memory/allocator.h>
+#include <__memory/uninitialized_algorithms.h>
+#include <__utility/move.h>
+#include <__utility/swap.h>
 #include <cmath>
 #include <cstddef>
-#include <functional>
+#include <functional> // TODO: Remove this include
 #include <initializer_list>
 #include <new>
 #include <version>
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.transform/ranges.transform.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.transform/ranges.transform.pass.cpp
--- a/libcxx/test/std/algorithms/alg.modifying.operations/alg.transform/ranges.transform.pass.cpp
+++ b/libcxx/test/std/algorithms/alg.modifying.operations/alg.transform/ranges.transform.pass.cpp
@@ -40,6 +40,7 @@
 #include <algorithm>
 #include <array>
 #include <cassert>
+#include <functional>
 #include <ranges>
 
 #include "test_iterators.h"
diff --git a/libcxx/test/std/algorithms/alg.nonmodifying/mismatch/ranges_mismatch.pass.cpp b/libcxx/test/std/algorithms/alg.nonmodifying/mismatch/ranges_mismatch.pass.cpp
--- a/libcxx/test/std/algorithms/alg.nonmodifying/mismatch/ranges_mismatch.pass.cpp
+++ b/libcxx/test/std/algorithms/alg.nonmodifying/mismatch/ranges_mismatch.pass.cpp
@@ -24,6 +24,7 @@
 #include <algorithm>
 #include <array>
 #include <cassert>
+#include <functional>
 #include <ranges>
 
 #include "test_iterators.h"
diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.min.max/ranges.max.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.min.max/ranges.max.pass.cpp
--- a/libcxx/test/std/algorithms/alg.sorting/alg.min.max/ranges.max.pass.cpp
+++ b/libcxx/test/std/algorithms/alg.sorting/alg.min.max/ranges.max.pass.cpp
@@ -28,6 +28,7 @@
 #include <algorithm>
 #include <array>
 #include <cassert>
+#include <functional>
 #include <ranges>
 
 #include "almost_satisfies_types.h"
diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.min.max/ranges.max_element.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.min.max/ranges.max_element.pass.cpp
--- a/libcxx/test/std/algorithms/alg.sorting/alg.min.max/ranges.max_element.pass.cpp
+++ b/libcxx/test/std/algorithms/alg.sorting/alg.min.max/ranges.max_element.pass.cpp
@@ -22,6 +22,7 @@
 #include <algorithm>
 #include <array>
 #include <cassert>
+#include <functional>
 #include <random>
 #include <ranges>
 
diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.min.max/ranges.min.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.min.max/ranges.min.pass.cpp
--- a/libcxx/test/std/algorithms/alg.sorting/alg.min.max/ranges.min.pass.cpp
+++ b/libcxx/test/std/algorithms/alg.sorting/alg.min.max/ranges.min.pass.cpp
@@ -26,6 +26,7 @@
 #include <algorithm>
 #include <array>
 #include <cassert>
+#include <functional>
 #include <ranges>
 
 #include "almost_satisfies_types.h"
diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.min.max/ranges.min_element.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.min.max/ranges.min_element.pass.cpp
--- a/libcxx/test/std/algorithms/alg.sorting/alg.min.max/ranges.min_element.pass.cpp
+++ b/libcxx/test/std/algorithms/alg.sorting/alg.min.max/ranges.min_element.pass.cpp
@@ -22,6 +22,7 @@
 #include <algorithm>
 #include <array>
 #include <cassert>
+#include <functional>
 #include <random>
 #include <ranges>
 
diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.min.max/ranges.minmax.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.min.max/ranges.minmax.pass.cpp
--- a/libcxx/test/std/algorithms/alg.sorting/alg.min.max/ranges.minmax.pass.cpp
+++ b/libcxx/test/std/algorithms/alg.sorting/alg.min.max/ranges.minmax.pass.cpp
@@ -28,6 +28,7 @@
 #include <algorithm>
 #include <array>
 #include <cassert>
+#include <functional>
 #include <ranges>
 
 #include "test_iterators.h"
diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.min.max/ranges.minmax_element.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.min.max/ranges.minmax_element.pass.cpp
--- a/libcxx/test/std/algorithms/alg.sorting/alg.min.max/ranges.minmax_element.pass.cpp
+++ b/libcxx/test/std/algorithms/alg.sorting/alg.min.max/ranges.minmax_element.pass.cpp
@@ -23,6 +23,7 @@
 #include <algorithm>
 #include <array>
 #include <cassert>
+#include <functional>
 #include <ranges>
 
 #include "almost_satisfies_types.h"
diff --git a/libcxx/test/std/ranges/range.adaptors/range.lazy.split/constraints.compile.pass.cpp b/libcxx/test/std/ranges/range.adaptors/range.lazy.split/constraints.compile.pass.cpp
--- a/libcxx/test/std/ranges/range.adaptors/range.lazy.split/constraints.compile.pass.cpp
+++ b/libcxx/test/std/ranges/range.adaptors/range.lazy.split/constraints.compile.pass.cpp
@@ -15,6 +15,7 @@
 //            (forward_range<V> || tiny-range<Pattern>)
 // class lazy_split_view;
 
+#include <functional>
 #include <ranges>
 
 #include "test_iterators.h"