Ben Gastauer (born 14 November 1987) is a Luxembourgish former professional road cyclist, who spent the whole of his 12 year professional career riding for the UCI WorldTeam Ag2r–La Mondiale. He took three professional victories during his career: the national time trial championship in 2012, and the general classification and a stage at the 2015 Tour du Haut Var. He was part of the AG2R squad that won the team classification and delivered Jean-Christophe Péraud to the podium at the 2014 Tour de France, and those which assisted Romain Bardet to podium finishes at the 2016 and 2017 Tours. In August 2021 the AG2R team announced that Gastauer would retire from competition at the end of the season due to a problem with his pelvic floor, finishing his career at the 2021 Tour de Luxembourg the following month.