Ian Hedworth John Little Gilmour, Baron Gilmour of Craigmillar, was a Conservative Party politician in the United Kingdom. He was styled Sir Ian Gilmour, 3rd Baronet from 1977, having succeeded to his father's baronetcy, until he became a life peer in 1992. He was Secretary of State for Defence in 1974, in the government of Edward Heath. In the government of Margaret Thatcher, he was Lord Privy Seal from 1979 to 1981.

The Secretary of State for Defence, also known as the Defence Secretary, is a secretary of state in the Government of the United Kingdom, with responsibility for the Ministry of Defence. As a senior minister, the incumbent is a member of the Cabinet of the United Kingdom.