diff --git a/.appveyor.yml b/.appveyor.yml
index 6586dd60..6329d249 100644
--- a/.appveyor.yml
+++ b/.appveyor.yml
@@ -12,7 +12,7 @@ install:
 build_script:
   - mkdir build
   - cd build
-  - cmake .. -DCLI_SINGLE_FILE_TESTS=ON -DCMAKE_BUILD_TYPE=Debug -DCMAKE_GENERATOR="Visual Studio 14 2015"
+  - cmake .. -DCLI11_SINGLE_FILE_TESTS=ON -DCMAKE_BUILD_TYPE=Debug -DCMAKE_GENERATOR="Visual Studio 14 2015"
   - cmake --build .
   - cd ..
   - conan create . CLIUtils/CLI11
diff --git a/.ci/make_and_test.sh b/.ci/make_and_test.sh
index 18b88895..2ba81aee 100755
--- a/.ci/make_and_test.sh
+++ b/.ci/make_and_test.sh
@@ -5,7 +5,7 @@ set -evx
 
 mkdir -p build
 cd build
-cmake .. -DCLI_CXX_STD=$1 -DCLI_SINGLE_FILE_TESTS=ON -DCMAKE_BUILD_TYPE=Debug -DCMAKE_CXX_COMPILER_LAUNCHER=ccache
+cmake .. -DCLI11_CXX_STD=$1 -DCLI11_SINGLE_FILE_TESTS=ON -DCMAKE_BUILD_TYPE=Debug -DCMAKE_CXX_COMPILER_LAUNCHER=ccache
 cmake --build . -- -j2
 
 set +evx
diff --git a/.ci/run_codecov.sh b/.ci/run_codecov.sh
index 2bf47e53..28d149a5 100755
--- a/.ci/run_codecov.sh
+++ b/.ci/run_codecov.sh
@@ -7,9 +7,9 @@ set -evx
 cd ${TRAVIS_BUILD_DIR}
 mkdir -p build
 cd build
-cmake .. -DCLI_SINGLE_FILE_TESTS=OFF -DCLI_EXAMPLES=OFF -DCMAKE_BUILD_TYPE=Coverage
+cmake .. -DCLI11_SINGLE_FILE_TESTS=OFF -DCLI11_EXAMPLES=OFF -DCMAKE_BUILD_TYPE=Coverage
 cmake --build . -- -j2
-cmake --build . --target CLI_coverage
+cmake --build . --target CLI11_coverage
 
 set +evx
 echo -en "travis_fold:end:script.build\\r"
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 7fd2f5db..de2f8ae9 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -16,10 +16,10 @@ set(CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake" ${CMAKE_MODULE_PATH})
 # Only if built as the main project
 if(CMAKE_PROJECT_NAME STREQUAL PROJECT_NAME)
     # User settable
-    set(CLI_CXX_STD "11"  CACHE STRING "The CMake standard to require")
+    set(CLI11_CXX_STD "11"  CACHE STRING "The CMake standard to require")
 
     set(CUR_PROJ ON)
-    set(CMAKE_CXX_STANDARD ${CLI_CXX_STD})
+    set(CMAKE_CXX_STANDARD ${CLI11_CXX_STD})
     set(CMAKE_CXX_EXTENSIONS OFF)
     set(CMAKE_CXX_STANDARD_REQUIRED ON)
 
@@ -56,10 +56,10 @@ set_property(GLOBAL PROPERTY USE_FOLDERS ON)
 
 if(CMAKE_BUILD_TYPE STREQUAL Coverage)
     include(CodeCoverage)
-    setup_target_for_coverage(CLI_coverage ctest coverage)
+    setup_target_for_coverage(CLI11_coverage ctest coverage)
 endif()
 
-file(GLOB CLI_headers "${CMAKE_CURRENT_SOURCE_DIR}/include/CLI/*")
+file(GLOB CLI11_headers "${CMAKE_CURRENT_SOURCE_DIR}/include/CLI/*")
 # To see in IDE, must be listed for target
 
 add_library(CLI11 INTERFACE)
@@ -113,18 +113,18 @@ export(PACKAGE CLI11)
 # Single file test
 find_package(PythonInterp)
 if(CUR_PROJ AND PYTHONINTERP_FOUND)
-    set(CLI_SINGLE_FILE_DEFAULT ON)
+    set(CLI11_SINGLE_FILE_DEFAULT ON)
 else()
-    set(CLI_SINGLE_FILE_DEFAULT OFF)
+    set(CLI11_SINGLE_FILE_DEFAULT OFF)
 endif()
 
-option(CLI_SINGLE_FILE "Generate a single header file" ${CLI_SINGLE_FILE_DEFAULT})
-if(CLI_SINGLE_FILE)
+option(CLI11_SINGLE_FILE "Generate a single header file" ${CLI11_SINGLE_FILE_DEFAULT})
+if(CLI11_SINGLE_FILE)
     find_package(PythonInterp REQUIRED)
     file(MAKE_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/include")
     add_custom_command(OUTPUT "${CMAKE_CURRENT_BINARY_DIR}/include/CLI11.hpp"
         COMMAND "${PYTHON_EXECUTABLE}" "${CMAKE_CURRENT_SOURCE_DIR}/scripts/MakeSingleHeader.py" "${CMAKE_CURRENT_BINARY_DIR}/include/CLI11.hpp"
-        DEPENDS "${CMAKE_CURRENT_SOURCE_DIR}/include/CLI/CLI.hpp" ${CLI_headers}
+        DEPENDS "${CMAKE_CURRENT_SOURCE_DIR}/include/CLI/CLI.hpp" ${CLI11_headers}
         )
     add_custom_target(generate_cli_single_file ALL
         DEPENDS "${CMAKE_CURRENT_BINARY_DIR}/include/CLI11.hpp")
@@ -134,25 +134,25 @@ if(CLI_SINGLE_FILE)
     add_library(CLI11_SINGLE INTERFACE)
     target_link_libraries(CLI11_SINGLE INTERFACE CLI11)
     add_dependencies(CLI11_SINGLE generate_cli_single_file)
-    target_compile_definitions(CLI11_SINGLE INTERFACE -DCLI_SINGLE_FILE)
+    target_compile_definitions(CLI11_SINGLE INTERFACE -DCLI11_SINGLE_FILE)
     target_include_directories(CLI11_SINGLE INTERFACE "${CMAKE_CURRENT_BINARY_DIR}/include/")
 endif()
 
-option(CLI_SINGLE_FILE_TESTS "Duplicate all the tests for a single file build" OFF)
+option(CLI11_SINGLE_FILE_TESTS "Duplicate all the tests for a single file build" OFF)
 
-option(CLI_TESTING "Build the tests and add them" ${CUR_PROJ})
-if(CLI_TESTING)
+option(CLI11_TESTING "Build the tests and add them" ${CUR_PROJ})
+if(CLI11_TESTING)
     enable_testing()
     add_subdirectory(tests)
 endif()
 
-option(CLI_EXAMPLES "Build the examples" ${CUR_PROJ})
-if(CLI_EXAMPLES)
+option(CLI11_EXAMPLES "Build the examples" ${CUR_PROJ})
+if(CLI11_EXAMPLES)
     add_subdirectory(examples)
 endif()
 
 if(NOT CUR_PROJ)
-    mark_as_advanced(CLI_SINGLE_FILE_TESTS CLI_EXAMPLES CLI_TESTING)
+    mark_as_advanced(CLI11_SINGLE_FILE_TESTS CLI11_EXAMPLES CLI11_TESTING)
 endif()
 
 # Packaging support
diff --git a/conanfile.py b/conanfile.py
index 77e584f9..7a32f711 100644
--- a/conanfile.py
+++ b/conanfile.py
@@ -22,8 +22,8 @@ class HelloConan(ConanFile):
 
     def build(self): # this is not building a library, just tests
         cmake = CMake(self)
-        cmake.definitions["CLI_EXAMPLES"] = "OFF"
-        cmake.definitions["CLI_SINGLE_FILE"] = "OFF"
+        cmake.definitions["CLI11_EXAMPLES"] = "OFF"
+        cmake.definitions["CLI11_SINGLE_FILE"] = "OFF"
         cmake.configure()
         cmake.build()
         cmake.test()
diff --git a/docs/Doxyfile b/docs/Doxyfile
index 5363a26e..0e2a8c75 100644
--- a/docs/Doxyfile
+++ b/docs/Doxyfile
@@ -334,7 +334,7 @@ BUILTIN_STL_SUPPORT    = NO
 # enable parsing support.
 # The default value is: NO.
 
-CPP_CLI_SUPPORT        = NO
+CPP_CLI11_SUPPORT        = NO
 
 # Set the SIP_SUPPORT tag to YES if your project consists of sip (see:
 # http://www.riverbankcomputing.co.uk/software/sip/intro) sources only. Doxygen
diff --git a/examples/CMakeLists.txt b/examples/CMakeLists.txt
index c2eef50c..8c2f13b3 100644
--- a/examples/CMakeLists.txt
+++ b/examples/CMakeLists.txt
@@ -1,5 +1,5 @@
 function(add_cli_exe T)
-    add_executable(${T} ${ARGN} ${CLI_headers})
+    add_executable(${T} ${ARGN} ${CLI11_headers})
     target_link_libraries(${T} PUBLIC CLI11)
     set_target_properties(
          ${T} PROPERTIES
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 29011457..dcac95fa 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -1,7 +1,7 @@
 set(GOOGLE_TEST_INDIVIDUAL OFF)
 include(AddGoogletest)
 
-set(CLI_TESTS
+set(CLI11_TESTS
     HelpersTest
     IniTest
     SimpleTest
@@ -13,20 +13,20 @@ set(CLI_TESTS
     OptionalTest
     )
 
-set(CLI_MULTIONLY_TESTS
+set(CLI11_MULTIONLY_TESTS
     TimerTest
     )
 
 # Only affects current directory, so safe
 include_directories(${CMAKE_CURRENT_SOURCE_DIR})
 
-foreach(T ${CLI_TESTS})
+foreach(T ${CLI11_TESTS})
 
-    add_executable(${T} ${T}.cpp ${CLI_headers})
+    add_executable(${T} ${T}.cpp ${CLI11_headers})
     target_link_libraries(${T} PUBLIC CLI11)
     add_gtest(${T})
 
-    if(CLI_SINGLE_FILE AND CLI_SINGLE_FILE_TESTS)
+    if(CLI11_SINGLE_FILE AND CLI11_SINGLE_FILE_TESTS)
         add_executable(${T}_Single ${T}.cpp)
         target_link_libraries(${T}_Single PUBLIC CLI11_SINGLE)
         add_gtest(${T}_Single)
@@ -37,9 +37,9 @@ foreach(T ${CLI_TESTS})
 
 endforeach()
 
-foreach(T ${CLI_MULTIONLY_TESTS})
+foreach(T ${CLI11_MULTIONLY_TESTS})
 
-    add_executable(${T} ${T}.cpp ${CLI_headers})
+    add_executable(${T} ${T}.cpp ${CLI11_headers})
     target_link_libraries(${T} PUBLIC CLI11)
     add_gtest(${T})
 
diff --git a/tests/HelpTest.cpp b/tests/HelpTest.cpp
index 1c762ca7..52b566af 100644
--- a/tests/HelpTest.cpp
+++ b/tests/HelpTest.cpp
@@ -1,4 +1,4 @@
-#ifdef CLI_SINGLE_FILE
+#ifdef CLI11_SINGLE_FILE
 #include "CLI11.hpp"
 #else
 #include "CLI/CLI.hpp"
diff --git a/tests/SimpleTest.cpp b/tests/SimpleTest.cpp
index bc1f1ba0..d87495f3 100644
--- a/tests/SimpleTest.cpp
+++ b/tests/SimpleTest.cpp
@@ -1,4 +1,4 @@
-#ifdef CLI_SINGLE_FILE
+#ifdef CLI11_SINGLE_FILE
 #include "CLI11.hpp"
 #else
 #include "CLI/CLI.hpp"
diff --git a/tests/app_helper.hpp b/tests/app_helper.hpp
index 49ef7554..4280cc9e 100644
--- a/tests/app_helper.hpp
+++ b/tests/app_helper.hpp
@@ -1,6 +1,6 @@
 #pragma once
 
-#ifdef CLI_SINGLE_FILE
+#ifdef CLI11_SINGLE_FILE
 #include "CLI11.hpp"
 #else
 #include "CLI/CLI.hpp"