Rugby union in Cornwall is Cornwall's most popular spectator sport with a large following. The followers of the national side are dubbed Trelawny's Army. In 1991 and 1999 Cornwall won the County Championship final played at Twickenham Stadium, beating Yorkshire and Gloucestershire respectively to win the Cup. They had another strong spell in the 2010s, reaching seven of the eight finals contested between 2013 and 2022, winning four of them.

Rugby union at the 1908 Summer Olympics. The event was summarised under the "Football" heading along with association football. The host Great Britain was represented by Cornwall, the 1908 county champion. Defending Olympic champions France withdrew, leaving Australasia, as the only other remaining entrant.