diff --git a/cmsis/CMSIS_5/CMSIS/RTOS2/RTX/CMakeLists.txt b/cmsis/CMSIS_5/CMSIS/RTOS2/RTX/CMakeLists.txt
index 24d9f345c3d..2a3d39f2790 100644
--- a/cmsis/CMSIS_5/CMSIS/RTOS2/RTX/CMakeLists.txt
+++ b/cmsis/CMSIS_5/CMSIS/RTOS2/RTX/CMakeLists.txt
@@ -15,6 +15,8 @@ function(_mbed_get_cortex_m_exception_handlers toolchain_dir)
             set(STARTUP_RTX_FILE TARGET_M3/irq_cm3.S)
         elseif(${key} STREQUAL M33)
             set(STARTUP_RTX_FILE TARGET_M33/irq_armv8mml.S)
+        elseif(${key} STREQUAL M55)
+            set(STARTUP_RTX_FILE TARGET_M33/irq_armv8mml.S)
         elseif(${key} STREQUAL RTOS_M4_M7)
             set(STARTUP_RTX_FILE TARGET_RTOS_M4_M7/irq_cm4f.S)
         endif()
diff --git a/tools/cmake/cores/Cortex-M55.cmake b/tools/cmake/cores/Cortex-M55.cmake
new file mode 100644
index 00000000000..88bb9b99495
--- /dev/null
+++ b/tools/cmake/cores/Cortex-M55.cmake
@@ -0,0 +1,28 @@
+# Copyright (c) 2021 ARM Limited. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+
+# Sets cpu core options
+if(${MBED_TOOLCHAIN} STREQUAL "GCC_ARM")
+    list(APPEND common_options
+        "-mthumb"
+        "-mfpu=fpv5-sp-d16"
+        "-mfloat-abi=softfp"
+        "-mcpu=cortex-m55"
+    )
+elseif(${MBED_TOOLCHAIN} STREQUAL "ARM")
+    list(APPEND common_options
+        "-mfpu=fpv5-sp-d16"
+        "-mfloat-abi=hard"
+        "-mcpu=cortex-m55"
+    )
+endif()
+
+function(mbed_set_cpu_core_definitions target)
+    target_compile_definitions(${target}
+        INTERFACE
+            __CORTEX_M55
+            __FPU_PRESENT=1
+            __CMSIS_RTOS
+            __MBED_CMSIS_RTOS_CM
+    )
+endfunction()
diff --git a/tools/cmake/toolchain.cmake b/tools/cmake/toolchain.cmake
index ff64de55e20..8d151ecc08f 100644
--- a/tools/cmake/toolchain.cmake
+++ b/tools/cmake/toolchain.cmake
@@ -53,6 +53,8 @@ elseif (MBED_CPU_CORE STREQUAL Cortex-M4)
     set(CMAKE_SYSTEM_PROCESSOR cortex-m4)
 elseif (MBED_CPU_CORE STREQUAL Cortex-M4F)
     set(CMAKE_SYSTEM_PROCESSOR cortex-m4)
+elseif (MBED_CPU_CORE STREQUAL Cortex-M55)
+    set(CMAKE_SYSTEM_PROCESSOR cortex-m55)
 elseif (MBED_CPU_CORE STREQUAL Cortex-M7)
     set(CMAKE_SYSTEM_PROCESSOR cortex-m7)
 elseif (MBED_CPU_CORE STREQUAL Cortex-M7F)