diff --git a/cmake/modules/kconfig.cmake b/cmake/modules/kconfig.cmake
index 65b3bbb0382..def17f16ae6 100644
--- a/cmake/modules/kconfig.cmake
+++ b/cmake/modules/kconfig.cmake
@@ -135,6 +135,9 @@ else()
   set(_local_TOOLCHAIN_HAS_PICOLIBC n)
 endif()
 
+# APP_DIR: Path to the main image (sysbuild) or synonym for APPLICATION_SOURCE_DIR (non-sysbuild)
+zephyr_get(APP_DIR VAR APP_DIR APPLICATION_SOURCE_DIR)
+
 set(COMMON_KCONFIG_ENV_SETTINGS
   PYTHON_EXECUTABLE=${PYTHON_EXECUTABLE}
   srctree=${ZEPHYR_BASE}
@@ -142,6 +145,7 @@ set(COMMON_KCONFIG_ENV_SETTINGS
   APPVERSION=${APP_VERSION_STRING}
   APP_VERSION_EXTENDED_STRING=${APP_VERSION_EXTENDED_STRING}
   APP_VERSION_TWEAK_STRING=${APP_VERSION_TWEAK_STRING}
+  APP_DIR=${APP_DIR}
   CONFIG_=${KCONFIG_NAMESPACE}_
   KCONFIG_CONFIG=${DOTCONFIG}
   KCONFIG_BOARD_DIR=${KCONFIG_BOARD_DIR}