Sir David Douglas Reid, 1st Baronet, JP (24 August 1872 – 23 March 1939) was the Unionist Member of Parliament for Down from 1922 until his death in 1939. Only son of Joseph Reid, of 22 Elmwood Avenue, Belfast, he attended Queens College, Belfast and New College, Oxford, graduating with 1st Class Honours in History. He then became a barrister at the Inner Temple and was called to the Bar in 1898. He contested East Tyrone in 1910 before becoming a Unionist Member of Parliament (MP) for East Down from 1918 to 1922, when the constituency was abolished. He was Chairman of the Ulster Unionist Party at Westminster.