Sam William Gagner (born August 10, 1989 in London, Ontario) is a Canadian professional ice hockey centre currently playing with the Edmonton Oilers of the National Hockey League (NHL).

Gagner played midget hockey with the Toronto Marlboros of the Greater Toronto Hockey League in 2004–05. He scored 173 points and was awarded the Buck Houle Award – a Marlboros team award given for outstanding on ice performance and leadership. The same season, he made his junior debut, playing 13 games for the Milton Icehawks of the OPJHL, scoring 15 points. In 2005–06, he joined the Sioux City Musketeers of the United States Hockey League and scored 46 points in 56 games, second in team scoring.

Gagner originally committed to play hockey at the collegiate level for the University of Wisconsin–Madison, but later decided to play closer to home and play major junior hockey in Canada. Considered a first round talent, the London Knights took him in the fourth round of the 2006 OHL entry draft on a flyer, as his commitment to play college hockey deterred many OHL teams from drafting him. Joined by future NHL stars Patrick Kane and Sergei Kostitsyn on the Knights' top line in 2006–07, Gagner scored 118 points in 53 games, fifth in league scoring. He also captained Team Burns/Bergeron (Red) in the 2007 CHL Top Prospects Game to a 5-3 victory over Team Bowman/Demers (White).