Martha MacKenzie (also Stewart and Holden) is a fictional character from the Australian Channel Seven soap opera Home and Away, played by Jodi Gordon. Martha made her first on-screen appearance on 8 September 1988. She was originally played by Burcin Kapkin. In 2005, the character returned to Home and Away, played by Jodi Gordon. Gordon was a model and she took acting lessons before auditioning for the role. Gordon won a Logie Award for "Most Popular New Female Talent" in 2006 and she earned several more award nominations for her portrayal of Martha. Martha returned on screen on 30 March 2005.

Martha was described as being friendly, feisty and fun loving. Martha's appearance has evolved throughout her time in the show: she was initially a tomboy who loved sport, but she later became a stylish woman. Upon her return in March 2005, Martha's storylines saw her surviving a helicopter crash, having an abortion and a miscarriage, battling alcoholism, being diagnosed with breast cancer and becoming a widow after her husband was shot. In a controversial storyline Martha worked as a pole dancer; the scenes were criticised by the broadcasting regulator for their content. Whilst playing Martha, Gordon was at the center of a number of personal scandals, which put her future in the show in doubt. In January 2010, it was announced that Gordon was leaving the show and Martha departed on 9 June 2010.