Darby Briton Loudon (12 March 1897 – c. 1963) was a New Zealand born rugby union player, a flanker who made sixteen representative appearances for the New South Wales state team in the 1920s. Four of these matches have since been decreed as Test matches by the Australian Rugby Union and Loudon, who led the side in one such match in 1922, was therefore a captain of the Australian national team.