Thomas Frank Brenchley (born 9 April 1918) was a British diplomat and Middle Eastern expert. During the 1960s he headed the Foreign Office's Arabian Department before becoming Assistant Under-Secretary of State. During the 1980s and '90s he chaired the Institute for the Study of Conflict and its successor organisation the Research Institute for the Study of Conflict and Terrorism.
Served with Royal Corps of Signals, 1939–46; Major on Staff of Military Attaché, Ankara, 1943–45; Director, Telecommunications Liaison Directorate, Syria and Lebanon, 1945–46. Civil Servant, GCHQ, 1947; transferred to Foreign Office, 1949; First Secretary: Singapore, 1950–53; Cairo, 1953–56; FO, 1956–58; Middle East Centre for Arab Studies, 1958–60; Counsellor, Khartoum, 1960–63; Chargé d’Affaires, Jedda, 1963; Head of Arabian Department, Foreign Office, 1963–67; Assistant Under-Secretary of State, Foreign Office, 1967–68; Ambassador to: Norway, 1968–72; Poland, 1972–74; Visiting Fellow, Institute for the Study of Conflict, 1974–75; Departmental Secretary, Cabinet Office, 1975–76. Dep. Sec. Gen. and Chief Exec., Arab-British Chamber of Commerce, 1976–83; Chairman: Institute for the Study of Conflict, 1983–89; Research Institute for the Study of Conflict and Terrorism, 1989–94; Pres., International Institute for Study of Conflict, Geneva, 1989–91. Dir, Center for Security Studies, Washington DC, 1988–90 
- ‘BRENCHLEY, Dr Thomas Frank’, Who's Who 2008, A & C Black, 2008; online edn, Oxford University Press, Dec 2007