The Secretary of State for Defence is the senior United Kingdom government minister in charge of the Ministry of Defence.

The post was created on 1 April 1964 and combined the former cabinet positions of First Lord of the Admiralty, Secretary of State for War and Secretary of State for Air. The separate offices of the Admiralty, War Office and the Air Ministry were abolished and their functions transferred to an expanded Ministry of Defence.

• Peter Thorneycroft (April 1, 1964–October 16, 1964)
• Denis Healey (October 16, 1964–June 19, 1970)
• Peter Carington, Lord Carrington (June 20, 1970–January 8, 1974)
• Ian Gilmour (January 8, 1974–March 4, 1974)
• Roy Mason (March 5, 1974–September 10, 1976)
• Frederick Mulley (September 10, 1976–May 4, 1979)
• Francis Pym (May 5, 1979–January 5, 1981)
• John Nott (January 5, 1981–January 6, 1983)
• Michael Heseltine (January 6, 1983–January 7, 1986) (Resigned)
• George Younger (January 9, 1986–July 24, 1989)
• Tom King (July 24, 1989–April 10, 1992)
• Malcolm Rifkind (April 10, 1992–July 5, 1995)
• Michael Portillo (July 5, 1995–May 2, 1997)
• George Robertson (Lord Robertson of Port Ellen) (May 3, 1997–October 11, 1999)
• Geoff Hoon (October 11, 1999—)