Robert Cochran Duncan (September 21, 1885 – May 4, 1957) was a British athlete. He competed at the 1908 Summer Olympics in London at the 1912 Summer Olympics in Stockholm.
In the 100 metres, Duncan won his first round heat with a time of 11.4 seconds to advance to the semifinals. There, he finished fourth and last in his semifinal heat to be eliminated.
He was not as successful in the 200 metres. His time of 23.1 seconds put him in second place behind Georges Malfait and eliminated him from competition.