Marlon Ronald Devonish, is an English former sprinter who competed in the 100 metres and 200 metres. A prodigious relay runner with particular strength as a 'bend' runner, Devonish ran the third leg for the Great Britain quartet which won the 4 x 100 metres at the 2004 Olympic Games, and won four World Championship medals in the same event in 1999, 2005, 2007 and 2009.
He is a member of the Coventry Godiva Harriersathletics club and was coached by Tony Lester. Early in his career he was successful at both 100 and 200-metre distances, winning English Schools and European Junior titles at both, but in later years he concentrated mostly on the longer distance. He was also a regular member of both the British and, at the Commonwealth Games, English 4 x 100-metre sprint relay teams, to some considerable success. He is a current Commonwealth Games record holder in the relay event. The most notable achievement of his career came at the 2004 Summer Olympics in Athens. There Devonish, along with Jason Gardener, Darren Campbell and Mark Lewis-Francis, won a gold medal in the 4 x 100 m. relay, where the quartet defeated the pre-race favourites, United States team, by just 0.01 seconds, in a season's best of 38.07. At the British Championships in July 2006, Devonish became the first man since Linford Christie in 1988 to win both the 100 m and 200 m races at the event. At the championship finals, he took the bronze medal in the 200 m. Devonish retained his 100 m title at the British Championships the following year. For the 2007 season Devonish improved his performance in the 100 m with a new personal best and competed in this event at the 2007 World Championships in Osaka rather than the 200 m which he had previously specialised in. Devonish finished 6th in the 100 m final. Devonish represented Great Britain at the 2008 Summer Olympics in Beijing. He competed at the 4x100 metres relay together with Simeon Williamson, Tyrone Edgar and Craig Pickering. In their qualification heat they were disqualified and eliminated. He also took part in the 200 metres individual, finishing first with a time of 20.49 seconds in his first round heat. With 20.43 seconds in his second round he only placed fourth in his heat, but his time was among the four best losing times and enough to qualify for the semi-finals. There he came to 20.57 seconds and the seventh time in his race, which was not enough for the final. He competed at the 2009 Manchester City Games, finishing second in the 150 metres final in 15.07 seconds. He was beaten by Usain Bolt who ran a world best-beating time. On 22 August 2009, Devonish was a member of the Great Britain and Northern Ireland men's 4x100m relay team that took bronze at the IAAF World Championships in Berlin with a season's best of 38.02. Harry Aikines-Aryeetey, Simeon Williamson and Tyrone Edgar ran the other legs.