Simon Christopher Lessing, MBE, (born 12 February 1971) is a British triathlete who won five International Triathlon Union (ITU) world titles (1992, 1995(2), 1996 and 1998).
He also won races at 70.3 (Half Ironman), ITU long distance and Ironman-distance events.
He set an Olympic-distance world record in 1996, and is noted for his 2004 Ironman Lake Placid win, where he set a course record of 8:23:12.
In 2008 he retired from professional racing.
Simon resides in Boulder, Colorado, United States, where he operates Boulder Coaching with Darren de Reuck.