Once a Jolly Swagman (U.S. title: Maniacs on Wheels) is a 1949 British film starring Dirk Bogarde, Bonar Colleano, Bill Owen, Thora Hird and Sid James. It was written by William Rose and Jack Lee, based on the 1944 novel of the same title by Montagu Slater.

It is centred on the sport of motorcycle speedway racing, which was at its peak of popularity at the time.

The title of the film refers to the first line of the Australian song "Waltzing Matilda".