[5] The current secretary of state for defence is John Healey, who was appointed on 5 July 2024 following the 2024 United Kingdom general election.

It was established by the prime minister, Stanley Baldwin, in response to criticism that Britain's armed forces were understrength compared to those of Nazi Germany.

When the Second World War broke out, the new prime minister Neville Chamberlain formed a small War Cabinet and it was expected that the minister would serve as a spokesperson for the three service ministers, the secretary of state for war, the first lord of the admiralty and the secretary of state for air; however, political considerations resulted in all three posts being included in the Cabinet, and this role proved increasingly redundant.

The post was created in response to previous criticism that there had been no clear single minister in charge of the prosecution of World War II.

In 1946, the post became the only cabinet-level post representing the military, with the three service ministers – the secretary of state for war, the first lord of the admiralty, and the secretary of state for air, now formally subordinated to the minister of defence.