David Forsyth Main (1831 – 27 July 1880) was a 19th-century member of parliament in Otago, New Zealand. Main was one of three candidates in the Gold Field Towns electorate in the 1866 election, when he came a close second to James Benn Bradshaw. Main represented the Port Chalmers electorate from 1867 to 1870, when he retired. He was a barrister and died in Dunedin aged 48y.