Karl Alzner (born September 24, 1988) is a Canadian professional ice hockey defenceman, currently playing for the Washington Capitals. He was drafted in the first round, 5th overall, by the Capitals in the 2007 NHL Entry Draft. A standout in junior, Alzner won two World Junior Hockey Championship gold medals with team Canada (as the captain), and was named the Western Hockey League (WHL)'s top player and Canadian Hockey League (CHL)'s top defenceman in 2008.