Martin John Kemp (born 10 October 1961) is an English musician and actor, best known as the bassist in the new wave band Spandau Ballet and for his role as Steve Owen in EastEnders.

He is the younger brother of Gary Kemp, who is also a member of Spandau Ballet and an actor. In 2012, Kemp finished third in the tenth series of Celebrity Big Brother, and in 2017 he appeared as a judge on the BBC series Let It Shine.

Kemp was born to Frank and Eileen Kemp at their house in Islington, north London, and attended Rotherfield Junior School. From the age of 7 he attended the Anna Scher Theatre drama club with his brother Gary, and appeared in many TV shows, including Jackanory, The Tomorrow People and Dixon of Dock Green. In his last year with Anna Scher, he won a role in an episode of the BBC television series The Glittering Prizes, appearing alongside Tom Conti and Nigel Havers in 1976.

Kemp grew up in north London and attended Central Foundation Boys' School, Islington. After leaving school at 16, he began an apprenticeship in a print factory, but soon became disenchanted.

Kemp's life changed when Steve Dagger, the manager of his brother Gary's band the Gentry, suggested Martin should replace the band's bass-player. Kemp learned to play bass in three months and performed for the first time with the Gentry at a college party. Eventually the band was renamed Spandau Ballet and Kemp left his printing job to concentrate on the band full-time.

Spandau Ballet went on to have a great deal of success in the New Romantic era, with four of their albums reaching the top ten of the UK Albums Chart. True also gave the band their first UK number-one album and, with the album's title track, single. Kemp also performed with the band on the popular 1984 famine-relief-project song "Do They Know It's Christmas?", written by Bob Geldof and Midge Ure. Because of a dispute over royalties, the band split up in the early 1990s.

Spandau Ballet announced they had reformed at a press conference on HMS Belfast on 25 March 2009. The band also announced a world tour, beginning with dates in the UK and Ireland in October 2009.

Kemp and his brother Gary returned to acting in 1990, both appearing in the British film The Krays, in which they played the notorious gangster twins Ronald and Reginald Kray. Their performances received a great deal of critical acclaim. After The Krays, Martin Kemp moved to Los Angeles in the early 1990s and made appearances in television series such as The Outer Limits and Highlander: The Series. He also appeared in several Hollywood films, including Waxwork II: Lost in Time (1992) and Embrace of the Vampire (1994).