Malcolm Ian Sinclair, 20th Earl of Caithness, PC (born 3 November 1948), is a Scottish Conservative politician and member of the House of Lords as one of the remaining hereditary peers.

Sinclair's mother was possibly descended from the de Pury family of Neuchâtel, Switzerland, who were members of the Prussian nobility.

He was, however, elected as one of the 90 representative peers designed under the provisions of the act to remain in the House of Lords.

He serves as chief executive and has been responsible for getting the castle listed by the World Monuments Fund in its Watch List of the 100 Most Endangered Sites in the World in 2002, the fundraising and overseeing the remedial works which has allowed the castle to be accessible and open to the public.

They had two children:[4] In January 1994, Caithness resigned from his post at the Ministry of Transport, following the suicide of his wife.

[5] In November 2004 he married secondly Leila Cassel Jenkins, whom he had met at Ascot, in Rosslyn Chapel.