Erik Sven Gunnar Karlsson (pronounced ; born 31 May 1990) is a Swedish professional ice hockey player who serves as captain of the Ottawa Senators of the National Hockey League (NHL). Karlsson was drafted in the first round, 15th overall, by the Senators at the 2008 NHL Entry Draft. Karlsson is a two-time winner of the James Norris Memorial Trophy as the NHL's best defenceman, winning the award in 2012 and 2015.
Karlsson made his Elitserien debut for Frölunda HC on 1 March 2008, recording 8:48 of ice time during a sold out home game in Scandinavium, against league leaders HV71. Karlsson scored the game-winning goal, assisted by Tomi Kallio and Magnus Kahnberg, with a slapshot in overtime during a man advantage. The win secured a playoff berth for Frölunda with three games remaining in the regular season.
Karlsson finished the season with Frölunda's J20 team playing in the J20 SuperElit playoffs, where Frölunda took home the Anton Cup when they won, two games to one, against Brynäs IF in the Swedish Junior Ice Hockey Championship final.