diff --git a/CMakeLists.txt b/CMakeLists.txt
index 01808e2d74e..2a9522ec061 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -183,7 +183,6 @@ add_link_options(-Wno-unused-command-line-argument)
 
 include_directories(.)
 include_directories(Userland/Libraries)
-include_directories(Userland/Libraries/LibC)
 include_directories(Userland/Libraries/LibCrypt)
 include_directories(Userland/Libraries/LibSystem)
 include_directories(Userland/Services)
diff --git a/Kernel/CMakeLists.txt b/Kernel/CMakeLists.txt
index 1aceb78b85b..ea039070886 100644
--- a/Kernel/CMakeLists.txt
+++ b/Kernel/CMakeLists.txt
@@ -693,9 +693,10 @@ add_compile_definitions(KERNEL)
 add_link_options(LINKER:-z,notext)
 
 add_library(kernel_heap STATIC ${KERNEL_HEAP_SOURCES})
+add_dependencies(kernel_heap install_libc_headers)
 
 add_executable(Kernel ${SOURCES})
-add_dependencies(Kernel generate_EscapeSequenceStateMachine.h generate_version_header)
+add_dependencies(Kernel generate_EscapeSequenceStateMachine.h generate_version_header install_libc_headers)
 
 if (NOT "${SERENITY_ARCH}" STREQUAL "aarch64")
     add_custom_command(
diff --git a/Kernel/Library/StdLib.h b/Kernel/Library/StdLib.h
index ead5b06c60d..d9572d998ec 100644
--- a/Kernel/Library/StdLib.h
+++ b/Kernel/Library/StdLib.h
@@ -13,6 +13,7 @@
 #include <AK/Userspace.h>
 #include <Kernel/Library/KString.h>
 #include <Kernel/UnixTypes.h>
+#include <stddef.h>
 
 ErrorOr<NonnullOwnPtr<Kernel::KString>> try_copy_kstring_from_user(Userspace<char const*>, size_t);
 ErrorOr<Duration> copy_time_from_user(timespec const*);
@@ -51,8 +52,6 @@ void const* memmem(void const* haystack, size_t, void const* needle, size_t);
 [[nodiscard]] inline u16 htons(u16 w) { return (w & 0xff) << 8 | ((w >> 8) & 0xff); }
 }
 
-#define offsetof(type, member) __builtin_offsetof(type, member)
-
 template<typename T>
 [[nodiscard]] inline ErrorOr<void> copy_from_user(T* dest, T const* src)
 {
diff --git a/Kernel/Prekernel/CMakeLists.txt b/Kernel/Prekernel/CMakeLists.txt
index a5d4cbc6b02..cdff1582a56 100644
--- a/Kernel/Prekernel/CMakeLists.txt
+++ b/Kernel/Prekernel/CMakeLists.txt
@@ -16,6 +16,7 @@ endif()
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -static")
 
 add_executable(${PREKERNEL_TARGET} ${SOURCES})
+add_dependencies(${PREKERNEL_TARGET} install_libc_headers)
 target_compile_options(${PREKERNEL_TARGET} PRIVATE -no-pie -fno-pic -fno-threadsafe-statics)
 
 target_link_options(${PREKERNEL_TARGET} PRIVATE LINKER:-T ${CMAKE_CURRENT_SOURCE_DIR}/linker.ld -nostdlib LINKER:--no-pie)
diff --git a/Userland/DynamicLoader/CMakeLists.txt b/Userland/DynamicLoader/CMakeLists.txt
index 761dfbdc9ec..b61ddad788f 100644
--- a/Userland/DynamicLoader/CMakeLists.txt
+++ b/Userland/DynamicLoader/CMakeLists.txt
@@ -47,6 +47,7 @@ if (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
 endif()
 
 add_executable(Loader.so ${SOURCES})
+add_dependencies(Loader.so install_libc_headers)
 
 if (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
     target_link_libraries(Loader.so PRIVATE gcc)
diff --git a/Userland/Libraries/LibC/CMakeLists.txt b/Userland/Libraries/LibC/CMakeLists.txt
index a0d388de548..b42fb30d076 100644
--- a/Userland/Libraries/LibC/CMakeLists.txt
+++ b/Userland/Libraries/LibC/CMakeLists.txt
@@ -76,6 +76,25 @@ set(LIBC_SOURCES
     wstdio.cpp
 )
 
+file(GLOB_RECURSE LIBC_HEADERS RELATIVE "${CMAKE_CURRENT_SOURCE_DIR}" CONFIGURE_DEPENDS "*.h")
+list(APPEND LIBC_HEADERS "../LibELF/ELFABI.h" "../LibRegex/RegexDefs.h")
+
+add_custom_target(install_libc_headers)
+
+# Copy LibC's headers into the sysroot to satisfy libc++'s include priority requirements.
+foreach(RELATIVE_HEADER_PATH IN LISTS LIBC_HEADERS)
+    get_filename_component(directory ${RELATIVE_HEADER_PATH} DIRECTORY)
+    string(REPLACE "../" "" subdirectory "${directory}")
+    file(MAKE_DIRECTORY "${CMAKE_STAGING_PREFIX}/${CMAKE_INSTALL_INCLUDEDIR}/${subdirectory}")
+    add_custom_command(
+        TARGET install_libc_headers
+        PRE_BUILD
+        COMMAND "${CMAKE_COMMAND}" -E copy_if_different "${RELATIVE_HEADER_PATH}" "${CMAKE_STAGING_PREFIX}/${CMAKE_INSTALL_INCLUDEDIR}/${subdirectory}"
+        WORKING_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}"
+        VERBATIM
+    )
+endforeach()
+
 file(GLOB ELF_SOURCES CONFIGURE_DEPENDS "../LibELF/*.cpp")
 
 if ("${SERENITY_ARCH}" STREQUAL "aarch64")
@@ -98,12 +117,14 @@ set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wno-unknown-warning-option")
 # Since all native serenity applications use dynamic libraries, prevent coverage on libc.a as well
 
 add_library(crt0 STATIC crt0.cpp)
+add_dependencies(crt0 install_libc_headers)
 target_link_libraries(crt0 PRIVATE NoCoverage)
 add_custom_command(
     TARGET crt0
     COMMAND "${CMAKE_COMMAND}" -E copy $<TARGET_OBJECTS:crt0> ${CMAKE_INSTALL_PREFIX}/usr/lib/crt0.o
 )
 add_library(crt0_shared STATIC crt0_shared.cpp)
+add_dependencies(crt0_shared install_libc_headers)
 target_link_libraries(crt0_shared PRIVATE NoCoverage)
 add_custom_command(
     TARGET crt0_shared
@@ -126,6 +147,7 @@ add_custom_command(
 
 set_source_files_properties (ssp_nonshared.cpp PROPERTIES COMPILE_FLAGS "-fno-stack-protector")
 add_library(ssp_nonshared STATIC ssp_nonshared.cpp)
+add_dependencies(ssp_nonshared install_libc_headers)
 target_link_libraries(ssp_nonshared PRIVATE NoCoverage)
 install(FILES ${CMAKE_CURRENT_BINARY_DIR}/libssp_nonshared.a DESTINATION ${CMAKE_INSTALL_PREFIX}/usr/lib/)
 
@@ -164,7 +186,7 @@ set_property(
 
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -nolibc")
 serenity_libc(LibC c)
-add_dependencies(LibC crti crt0 crt0_shared crtn)
+add_dependencies(LibC crti crt0 crt0_shared crtn install_libc_headers)
 target_link_libraries(LibC PRIVATE LibSystem LibTimeZone)
 
 # We mark LibCStatic as a dependency of LibC because this triggers the build of the LibCStatic target
diff --git a/Userland/Libraries/LibC/stddef.h b/Userland/Libraries/LibC/stddef.h
deleted file mode 100644
index 7d9655c3020..00000000000
--- a/Userland/Libraries/LibC/stddef.h
+++ /dev/null
@@ -1,20 +0,0 @@
-/*
- * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
- *
- * SPDX-License-Identifier: BSD-2-Clause
- */
-
-#pragma once
-
-#include <sys/cdefs.h>
-
-#define offsetof(type, member) __builtin_offsetof(type, member)
-
-#ifdef __cplusplus
-#    define NULL nullptr
-#else
-#    define NULL ((void*)0)
-#endif
-
-typedef __PTRDIFF_TYPE__ ptrdiff_t;
-typedef __SIZE_TYPE__ size_t;
diff --git a/Userland/Libraries/LibC/string.h b/Userland/Libraries/LibC/string.h
index 824c2d7c28f..23ec5ef69f9 100644
--- a/Userland/Libraries/LibC/string.h
+++ b/Userland/Libraries/LibC/string.h
@@ -12,6 +12,10 @@
 
 __BEGIN_DECLS
 
+#ifdef __cplusplus
+#    define __CORRECT_ISO_CPP_STRING_H_PROTO
+#endif
+
 // A few C Standard Libraries include this header in <string.h>, and hence expect
 // `strcasecmp` etcetera to be available as part of a <string.h> include, so let's
 // do the same here to maintain compatibility
diff --git a/Userland/Libraries/LibC/wchar.h b/Userland/Libraries/LibC/wchar.h
index 909b3b8aa27..b6052f7c81d 100644
--- a/Userland/Libraries/LibC/wchar.h
+++ b/Userland/Libraries/LibC/wchar.h
@@ -18,6 +18,10 @@ __BEGIN_DECLS
 #    define WEOF (0xffffffffu)
 #endif
 
+#ifdef __cplusplus
+#    define _LIBCPP_WCHAR_H_HAS_CONST_OVERLOADS
+#endif
+
 typedef __WINT_TYPE__ wint_t;
 typedef unsigned long int wctype_t;
 
diff --git a/Userland/Libraries/LibCrypt/CMakeLists.txt b/Userland/Libraries/LibCrypt/CMakeLists.txt
index 6ecc98ca1c4..46101c37f6c 100644
--- a/Userland/Libraries/LibCrypt/CMakeLists.txt
+++ b/Userland/Libraries/LibCrypt/CMakeLists.txt
@@ -3,6 +3,7 @@
 # To avoid a circular dependency chain with LibCrypt --> LibCrypto --> LibCore --> LibCrypt
 # We include the SHA2 implementation from LibCrypto here manually
 add_library(LibCryptSHA2 OBJECT ../LibCrypto/Hash/SHA2.cpp)
+add_dependencies(LibCryptSHA2 install_libc_headers)
 set_target_properties(LibCryptSHA2 PROPERTIES CXX_VISIBILITY_PRESET hidden)
 set_target_properties(LibCryptSHA2 PROPERTIES VISIBILITY_INLINES_HIDDEN ON)
 
diff --git a/Userland/Libraries/LibSanitizer/CMakeLists.txt b/Userland/Libraries/LibSanitizer/CMakeLists.txt
index 988e8b29710..fe43a55eb67 100644
--- a/Userland/Libraries/LibSanitizer/CMakeLists.txt
+++ b/Userland/Libraries/LibSanitizer/CMakeLists.txt
@@ -9,6 +9,8 @@ set_source_files_properties(../LibC/ssp_nonshared.cpp PROPERTIES COMPILE_FLAGS "
 
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -nostdlib")
 serenity_libc(LibUBSanitizer ubsan)
+add_dependencies(LibUBSanitizer install_libc_headers)
 
 add_library(LibUBSanitizerStatic STATIC ${SOURCES})
+add_dependencies(LibUBSanitizerStatic install_libc_headers)
 target_link_libraries(LibUBSanitizerStatic PRIVATE NoCoverage)
diff --git a/Userland/Libraries/LibSystem/CMakeLists.txt b/Userland/Libraries/LibSystem/CMakeLists.txt
index a8932887751..95992e7c234 100644
--- a/Userland/Libraries/LibSystem/CMakeLists.txt
+++ b/Userland/Libraries/LibSystem/CMakeLists.txt
@@ -4,8 +4,10 @@ set(SOURCES
 
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -nostdlib")
 serenity_libc(LibSystem system)
+add_dependencies(LibSystem install_libc_headers)
 target_include_directories(LibSystem PUBLIC ${CMAKE_CURRENT_SOURCE_DIR})
 
 add_library(LibSystemStatic STATIC ${SOURCES})
+add_dependencies(LibSystemStatic install_libc_headers)
 target_include_directories(LibSystemStatic PUBLIC ${CMAKE_CURRENT_SOURCE_DIR})
 target_link_libraries(LibSystemStatic PRIVATE NoCoverage)
diff --git a/Userland/Libraries/LibTest/CMakeLists.txt b/Userland/Libraries/LibTest/CMakeLists.txt
index 0800106eb40..a1ca2eea8f9 100644
--- a/Userland/Libraries/LibTest/CMakeLists.txt
+++ b/Userland/Libraries/LibTest/CMakeLists.txt
@@ -9,3 +9,8 @@ serenity_lib(LibTest test)
 
 add_library(LibTestMain OBJECT TestMain.cpp)
 add_library(JavaScriptTestRunnerMain OBJECT JavaScriptTestRunnerMain.cpp)
+
+if (SERENITYOS)
+    add_dependencies(LibTestMain install_libc_headers)
+    add_dependencies(JavaScriptTestRunnerMain install_libc_headers)
+endif()
diff --git a/Userland/Libraries/LibTimeZone/CMakeLists.txt b/Userland/Libraries/LibTimeZone/CMakeLists.txt
index c1e9f992ae4..a92f60a8b5b 100644
--- a/Userland/Libraries/LibTimeZone/CMakeLists.txt
+++ b/Userland/Libraries/LibTimeZone/CMakeLists.txt
@@ -13,3 +13,6 @@ target_compile_definitions(LibTimeZone PRIVATE ENABLE_TIME_ZONE_DATA=$<BOOL:${EN
 # NOTE: These objects are used by the DynamicLoader, which is always built without coverage instrumentation.
 #       We could allow them to be instrumented for coverage if DynamicLoader built its own copy
 target_link_libraries(LibTimeZone PRIVATE NoCoverage)
+if (SERENITYOS)
+    add_dependencies(LibTimeZone install_libc_headers)
+endif()