John William Steffensen (born 30 August 1982) is an Australian former track and field athlete, who specialised in 200 and 400 metres.

Born in Perth, Western Australia, to South African immigrant parents, Steffensen competed in the 2004 Olympics, and was a part of the Australian team that won the silver medal in the 4 × 400 metres relay.

Steffensen won the gold medal in the 400 m at the 2006 Commonwealth Games in Melbourne, with a time of 44.73, setting a new personal best.

[1] He won a second gold medal as the first runner in the 4 × 400 m Australian relay team at the 2006 Commonwealth Games.

He was runner up to Stephanie Rice in the 2013 Australian version of the television program Celebrity Apprentice.