Joost Posthuma (born 8 March 1981) is a Dutch retired professional road bicycle racer, who competed as a professional between 2004 and 2012. Born in Hengelo, Posthuma was known for his time-trialling and he wore the white jersey for the best young rider at the 2006 Tour de France. Posthuma set the best time for riders eligible for the young rider classification in the prologue, but lost it after the 1st road stage, after a rival got in a breakaway and got bonus seconds on the road.