John W. Peter Cawthorn (17 February 1931 – 1999) was an Australian amateur tennis player who later turned professional in 1953.

[2] Cawthorn played his first senior tournament in 1949 at the New South Wales Hard Court Championships where he reached the quarter finals.

[5] He also competed at 1952 Wimbledon Championships, where he was in the top half of the draw, but lost in the first round to the American player Harry Likas.

In 1953 Peter turned professional and played his first tournament at the Slazenger Pro Championships in Scarborough, England, where he reached the quarter finals before losing to Frank Sedgman.

[6] Peter Cawthorn announced his engagement to the English tennis player Lorna Cornell in January 1953,[20] and they married on 18 February 1953 in Kensington, London.