A GPT hidden partition locking key system includes a server device coupled to the key management system through a network. The server device includes a storage system having a GPT identifying data storage partitions included on a storage system and a hidden partition included on the storage system. A remote access controller device in the server device retrieves a partition locking key from the key management system and provides it for storage in the hidden partition. A BIOS in the server device includes a runtime service that receives a request to provide access for the operating system application to a first data storage partition, accesses the partition locking key in the hidden partition, and uses the partition locking key to unlock the first data storage partition to allow the operating system application to access data stored thereon.