Tyler Hamilton (born March 1, 1971, Marblehead, Massachusetts) is a former American professional road bicycle racer and former Olympic gold medalist. Hamilton became a professional cyclist in 1995, and during the 1999, 2000 and 2001 Tour de France was a teammate of Lance Armstrong who won those races.
Hamilton appeared at the 2000 Summer Olympics, and again at the 2004 Summer Olympics. In 2004, he won a gold medal at the time trial. The first doping test gave a positive result, but because the backup sample was frozen, no doping offence could be proven. After he failed further doping tests at the 2004 Vuelta a España, Hamilton was suspended for two years.
After his suspension, Hamilton came back and became national road race champion in 2008. In 2009, Hamilton failed a doping test again, and this time he was banned for eight years, which effectively caused him to retire. In July 2010, he was subpoenaed to appear before a grand jury revolving around the use of performance enhancing drugs in cycling. In May 2011, Hamilton admitted that he had used doping, and returned his gold medal. As of May 2011, the IOC has not removed him from the result, but is studying his confession.