Donald Henry Ewan McCowen (26 February 1908 – 5 September 1998) was a British rower who competed in the 1932 Summer Olympics. McCowen was born in Dublin, Ireland. He was educated at Cheltenham College and Cambridge University. In 1932 he was a member of the winning Cambridge boat in the Boat Race. The 1932 crew won the Grand Challenge Cup at Henley Royal Regatta rowing as Leander Club. They were subsequently chosen to represent Great Britain at the 1932 Summer Olympics in Los Angeles, where they came fourth in the eights.