Mark Downey (born 3 July 1996) is an Irish road and track cyclist, who currently rides for French amateur team Côtes d'Armor–Marie Morin–Véranda Rideau.

As a junior he competed at the 2014 UCI Road World Championships in the Men's junior time trial and also at the 2015 UCI Road World Championships in the Men's junior time trial.

On the track he competed at the 2015 UEC European Track Championships in the points race and team pursuit. He won the gold medal at the 2016–17 UCI Track Cycling World Cup, Round 2 in Apeldoorn in the points race. He also won the third round of the World Cup points race held in Cali, Colombia following that event he picked up a silver in the madison with his teammate Felix English. Concluding his 2017 World Cup campaign Downey won the madison in LA round 4 and was overall series winner in the points race.