Robert Michael Ryan (born February 20, 1978) is an American actor, producer, writer and director. His acting career spans a number of direct-to-video features and guest roles on a variety of popular TV series, perhaps most notably as Marvin Jr., brother of Jason Segel's Marshall Eriksen, on CBS' How I Met Your Mother (2005–12).

As a filmmaker, Ryan produced, wrote and directed Dark Revelations (2015), Ouija Witch (2023), Popeye the Slayer Man (2025) and its upcoming sequel.