Hubertus Martinus "Huub" Duyn (Dutch: Hubertus Martinus Duijn; born 1 September 1984 in Onderdijk, North Holland) is a Dutch former racing cyclist, who rode professionally between 2006 and 2019 for the Rabobank Continental Team, Garmin–Slipstream, Team NetApp, Donckers Koffie–Jelly Belly, Cyclingteam de Rijke, Vérandas Willems–Crelan and Roompot–Charles teams. His best result in his career was winning the Paris–Tours Espoirs in 2006. He currently works as a directeur sportif for UCI Women's WorldTeam Team Picnic–PostNL.