Twan Castelijns (born 23 January 1989 in Hapert) is a Dutch former cyclist, who rode professionally between 2014 and 2017 for the Koga Cycling Team, Baby-Dump Cyclingteam and LottoNL–Jumbo squads.
During his career, he contested two Grand Tours; the 2016 Giro d'Italia, and the 2017 Giro d'Italia.