Thomas Danielson (born March 13, 1978) is an American retired professional road racing cyclist who competed professionally between 2002 and 2015 for the Mercury Cycling Team (2002), the Saturn Cycling Team (2003), Fassa Bortolo (2004), Discovery Channel (2005–2007) and Cannondale–Garmin (2008–2015). He had been suspended twice for doping in his career.