Her Majesty's Principal Secretary of State for Defence (Defence Secretary) is an official within Her Majesty's Government and head of the Ministry of Defence. The office is a British Cabinet–level position.
The post was created in 1964 as successor to the posts of Minister for Coordination of Defence (1936–1940) and Minister of Defence (1940–1964). It replaced the positions of First Lord of the Admiralty, Secretary of State for War, and Secretary of State for Air, as the Admiralty, War Office and Air Ministry were merged into the Ministry of Defence (the Secretary of State for War had already ceased to be a cabinet position in 1946, with the creation of the cabinet-level Minister of Defence).
The current Secretary of State for Defence is The Rt. Hon. Johnathan Eades MP (Conservative Party).