Malcolm Ian Sinclair, 20th Earl of Caithness, PC (born 3 November 1948) is a British Conservative politician and member of the House of Lords as one of the remaining hereditary peers. He is also 20th Lord Berriedale, 15th Baronet Sinclair, of Canisbay, Co. Caithness, Nova Scotia, and chief of Clan Sinclair. He is the Chief Executive of the Clan Sinclair Trust.
Caithness was educated at Blairmore School, Aberdeenshire then Marlborough College and Royal Agricultural College, Cirencester.
Caithness served as a House of Lords government whip under Margaret Thatcher from 1984 to 1985. He then moved to the Department of Transport as a Parliamentary Under Secretary of State, serving until 1986 when he became a Minister of State at the Home Office. In 1988 he was once again moved, this time to be Minister of State at the Department of Environment. In 1989, he became Paymaster-General.In 1990, Caithness was again shuffled to the Foreign Office as a Minister of State, and then in 1992 back to the Department of Transport. He married Diana Caroline Coke (1953–1994) in 1975.