diff --git a/libc/CMakeLists.txt b/libc/CMakeLists.txt
--- a/libc/CMakeLists.txt
+++ b/libc/CMakeLists.txt
@@ -48,6 +48,21 @@
 # Path libc/scripts directory.
 set(LIBC_BUILD_SCRIPTS_DIR "${LIBC_SOURCE_DIR}/utils/build_scripts")
 
+# Defining a global namespace for enclose all libc functions.
+set(LIBC_CMAKE_NAMESPACE "" CACHE STRING "The namespace to use to enclose internal implementations. Must start with '__llvm_libc'." FORCE)
+
+if(LIBC_CMAKE_NAMESPACE)
+  set(LLVM_LIBC_NAMESPACE "${LIBC_CMAKE_NAMESPACE}")
+else()
+  set(LLVM_LIBC_NAMESPACE "__llvm_libc_${LLVM_VERSION_MAJOR}_${LLVM_VERSION_MINOR}_${LLVM_VERSION_PATCH}_${LLVM_VERSION_SUFFIX}")
+endif()
+
+if(NOT LLVM_LIBC_NAMESPACE MATCHES "^__llvm_libc")
+  message(FATAL_ERROR "Invalid LLVM_LIBC_NAMESPACE. Must start with '__llvm_libc' was '${LLVM_LIBC_NAMESPACE}'")
+endif()
+
+message(STATUS "Setting LLVM_LIBC_NAMESPACE namespace to '${LLVM_LIBC_NAMESPACE}'")
+
 # Flags to pass down to the compiler while building the libc functions.
 set(LIBC_COMPILE_OPTIONS_DEFAULT "" CACHE STRING "Architecture to tell clang to optimize for (e.g. -march=... or -mcpu=...)")
 
diff --git a/libc/cmake/modules/LLVMLibCCompileOptions.cmake b/libc/cmake/modules/LLVMLibCCompileOptions.cmake
new file mode 100644
--- /dev/null
+++ b/libc/cmake/modules/LLVMLibCCompileOptions.cmake
@@ -0,0 +1,11 @@
+function(add_namespace_compile_option target_name)
+    if(NOT LLVM_LIBC_NAMESPACE)
+        message(FATAL_ERROR "LLVM_LIBC_NAMESPACE is not defined.")
+    endif()
+
+    if(LLVM_COMPILER_IS_GCC_COMPATIBLE)
+        target_compile_options(${target_name} PRIVATE "-DLIBC_NAMESPACE=${LLVM_LIBC_NAMESPACE}")
+    elseif(MSVC)
+        target_compile_options(${target_name} PRIVATE "/DLIBC_NAMESPACE=${LLVM_LIBC_NAMESPACE}")
+    endif()
+endfunction()
diff --git a/libc/cmake/modules/LLVMLibCObjectRules.cmake b/libc/cmake/modules/LLVMLibCObjectRules.cmake
--- a/libc/cmake/modules/LLVMLibCObjectRules.cmake
+++ b/libc/cmake/modules/LLVMLibCObjectRules.cmake
@@ -178,6 +178,7 @@
         ${ADD_GPU_OBJ_HDRS}
       )
 
+      add_namespace_compile_option(${gpu_target_name})
       target_compile_options(${gpu_target_name} PRIVATE ${compile_options})
       target_include_directories(${gpu_target_name} PRIVATE ${include_dirs})
       target_compile_definitions(${gpu_target_name} PRIVATE LIBC_COPT_PUBLIC_PACKAGING)
@@ -245,6 +246,7 @@
     OBJECT
     ${CMAKE_CURRENT_BINARY_DIR}/stubs/${stub_filename}
   )
+  add_namespace_compile_option(${fq_target_name})
   target_compile_options(${fq_target_name} BEFORE PRIVATE
                          ${common_compile_options} -nostdlib)
   foreach(packaged_gpu_binary ${packaged_gpu_binaries})
@@ -265,6 +267,7 @@
       ${ADD_GPU_OBJ_SRCS}
       ${ADD_GPU_OBJ_HDRS}
     )
+    add_namespace_compile_option(${internal_target_name})
     target_compile_options(${internal_target_name} BEFORE PRIVATE
                            ${common_compile_options} --target=${LIBC_GPU_TARGET_TRIPLE})
     if(LIBC_GPU_TARGET_ARCHITECTURE_IS_AMDGPU)
@@ -364,6 +367,7 @@
         ${LIBC_INCLUDE_DIR}
     )
     target_compile_options(${fq_target_name} PRIVATE ${compile_options})
+    add_namespace_compile_option(${fq_target_name})
   endif()
 
   if(SHOW_INTERMEDIATE_OBJECTS)
@@ -644,6 +648,7 @@
       ${ADD_ENTRYPOINT_OBJ_SRCS}
       ${ADD_ENTRYPOINT_OBJ_HDRS}
     )
+    add_namespace_compile_option(${internal_target_name})
     target_compile_options(${internal_target_name} BEFORE PRIVATE ${common_compile_options})
     target_include_directories(${internal_target_name} PRIVATE ${include_dirs})
     add_dependencies(${internal_target_name} ${full_deps_list})
@@ -657,6 +662,7 @@
       ${ADD_ENTRYPOINT_OBJ_SRCS}
       ${ADD_ENTRYPOINT_OBJ_HDRS}
     )
+    add_namespace_compile_option(${fq_target_name})
     target_compile_options(${fq_target_name} BEFORE PRIVATE ${common_compile_options} -DLIBC_COPT_PUBLIC_PACKAGING)
     target_include_directories(${fq_target_name} PRIVATE ${include_dirs})
     add_dependencies(${fq_target_name} ${full_deps_list})
@@ -902,4 +908,5 @@
     ${target_name}
     BEFORE PRIVATE -fPIC ${LIBC_COMPILE_OPTIONS_DEFAULT}
   )
+  add_namespace_compile_option(${target_name})
 endfunction(add_redirector_object)
diff --git a/libc/cmake/modules/LLVMLibCRules.cmake b/libc/cmake/modules/LLVMLibCRules.cmake
--- a/libc/cmake/modules/LLVMLibCRules.cmake
+++ b/libc/cmake/modules/LLVMLibCRules.cmake
@@ -1,3 +1,4 @@
+include(LLVMLibCCompileOptions)
 include(LLVMLibCTargetNameUtils)
 include(LLVMLibCFlagRules)
 include(LLVMLibCObjectRules)
diff --git a/libc/cmake/modules/LLVMLibCTestRules.cmake b/libc/cmake/modules/LLVMLibCTestRules.cmake
--- a/libc/cmake/modules/LLVMLibCTestRules.cmake
+++ b/libc/cmake/modules/LLVMLibCTestRules.cmake
@@ -154,6 +154,7 @@
       ${LIBC_SOURCE_DIR}
       ${LIBC_INCLUDE_DIR}
   )
+  add_namespace_compile_option(${fq_build_target_name})
   target_compile_options(
     ${fq_build_target_name}
     PRIVATE -fpie ${LIBC_COMPILE_OPTIONS_DEFAULT}
@@ -407,6 +408,7 @@
   )
   add_dependencies(libc-fuzzer ${fq_target_name})
 
+  add_namespace_compile_option(${fq_target_name})
   target_compile_options(${fq_target_name}
     PRIVATE
     ${LIBC_FUZZER_COMPILE_OPTIONS})
@@ -522,6 +524,7 @@
       ${LIBC_SOURCE_DIR}
       ${LIBC_INCLUDE_DIR}
   )
+  add_namespace_compile_option(${fq_build_target_name})
   target_compile_options(${fq_build_target_name}
       PRIVATE -fpie -ffreestanding -fno-exceptions -fno-rtti ${INTEGRATION_TEST_COMPILE_OPTIONS})
   # The GPU build requires overriding the default CMake triple and architecture.
@@ -665,6 +668,7 @@
       PROPERTIES ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR})
   set_target_properties(${fq_target_name}.__libc__
       PROPERTIES ARCHIVE_OUTPUT_NAME ${fq_target_name}.libc)
+  add_namespace_compile_option(${fq_target_name}.__libc__)
 
   set(fq_build_target_name ${fq_target_name}.__build__)
   add_executable(
@@ -686,6 +690,7 @@
       ${LIBC_SOURCE_DIR}
       ${LIBC_INCLUDE_DIR}
   )
+  add_namespace_compile_option(${fq_build_target_name})
   target_compile_options(${fq_build_target_name}
       PRIVATE ${LIBC_HERMETIC_TEST_COMPILE_OPTIONS} ${HERMETIC_TEST_COMPILE_OPTIONS})
 
diff --git a/libc/src/__support/common.h b/libc/src/__support/common.h
--- a/libc/src/__support/common.h
+++ b/libc/src/__support/common.h
@@ -9,6 +9,10 @@
 #ifndef LLVM_LIBC_SUPPORT_COMMON_H
 #define LLVM_LIBC_SUPPORT_COMMON_H
 
+#ifndef LIBC_NAMESPACE
+#error "LIBC_NAMESPACE macro is not defined."
+#endif
+
 #include "src/__support/macros/attributes.h"
 #include "src/__support/macros/properties/architectures.h"
 
diff --git a/libc/test/UnitTest/CMakeLists.txt b/libc/test/UnitTest/CMakeLists.txt
--- a/libc/test/UnitTest/CMakeLists.txt
+++ b/libc/test/UnitTest/CMakeLists.txt
@@ -27,9 +27,11 @@
       ${TEST_LIB_HDRS}
     )
     target_include_directories(${lib} PUBLIC ${LIBC_SOURCE_DIR})
+    add_namespace_compile_option(${lib})
     target_compile_options(${lib} PRIVATE -fno-exceptions -fno-rtti)
   endforeach()
   target_include_directories(${name}.hermetic PRIVATE ${LIBC_BUILD_DIR}/include)
+  add_namespace_compile_option(${name}.hermetic)
   target_compile_options(${name}.hermetic
       PRIVATE ${LIBC_HERMETIC_TEST_COMPILE_OPTIONS} -ffreestanding -nostdinc++)