Defence (defense in the United States) in ice hockey is a player position whose primary responsibility is to prevent the opposing team from scoring. They are often referred to as defencemen, defensemen, D, D-men or "blueliners" (the latter a reference to the blue line in ice hockey which represents the boundary of the offensive zone; defencemen generally position themselves along the line to keep the puck in the zone). They were once called cover-point.

In regular play, two defencemen complement three forwards and a goaltender on the ice. Exceptions include overtime during the regular season and when a team is shorthanded (i.e. has been assessed a penalty), in which two defencemen are typically joined by only two forwards and a goaltender.

Each year the NHL, the premier ice hockey league in the world, presents the James Norris Memorial Trophy to the best defenceman in the league. Bobby Orr of the Boston Bruins – an eight-time Norris Trophy recipient – is often considered to be the greatest defenceman in NHL and ice hockey history. In addition to his Norris Trophy honours, he is the only defenceman in NHL history to capture the Art Ross Trophy as the league's leading scorer. In 1998, Orr was selected as the best defenceman of all-time (second overall player behind Wayne Gretzky) in The Hockey News' Top 100 NHL Players of all-time.

Erik Karlsson (born 31 May 1990) is a Swedish professional ice hockey defenceman, currently playing for the Ottawa Senators of the National Hockey League (NHL). He was selected 15th overall by the Senators in the 2008 NHL Entry Draft.

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 off a faceoff, in overtime during a man advantage. The win secured a playoff berth for Frölunda with three games remaining of 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 to one in games against Brynäs IF in the Swedish Junior Ice Hockey Championship final.

Prior to the 2008 NHL Entry Draft, Karlsson was ranked fourth among European skaters by the NHL's Central Scouting Service. He was drafted 15th overall by the Ottawa Senators, in front of their hometown fans at Scotiabank Place in Ottawa, Ontario. The selection was made by Ottawa's captain Daniel Alfredsson, a native of Gothenburg, who played for Frölunda before entering the NHL. Ottawa's general manager, Bryan Murray, traded Ottawa's first round pick, 18th overall, and their third round pick in 2009 to the Nashville Predators for the Predators' first round pick, 15th overall, to ensure that no other team would pick Karlsson before them.

Joe Finley (born June 29, 1987) is an American ice hockey defenseman. He is currently playing with the Buffalo Sabres of the National Hockey League (NHL). Finley was selected by the Washington Capitals in the 1st round (27th overall) of the 2005 NHL Entry Draft.

Finley missed the majority of the 2009-10 season on injured reserve when on November 21, 2009, in a game with the Stingrays against the Gwinnett Gladiators, he ruptured an artery in his hand which required surgery.

On September 18, 2011, Finley accepted an invitation to training camp by the Buffalo Sabres. He impressed enough that he was signed to an AHL contract, and assigned to the Rochester Americans. Through the first quarter of the season, Finley was impressive as one half of the Americans shut-down defensive pairing. He led the Amerks in +/- with a +10. The Sabres and Finley reached a three-year contract on November 28, 2011, that will allow Finley to be called up by Sabres organization.

Two days after the deal was completed, Finley was called up by the Sabres where he made his NHL debut against the Red Wings on 12/2/11. Finley was the 475th player to play in the NHL after starting his career in the ECHL.

Francis Bouillon (born October 17, 1975) is an American professional hockey defenseman for the Nashville Predators in the National Hockey League. Nicknames in English for Francis include "Cube" or "Soupy" (as a reference to bouillon cubes), "Frank the Tank", and "Franky B". In French, people call him "le petit guerrier" which means "the little warrior", due to his physical intensity and his small stature.

Bouillon was born in New York City to a French-Canadian mother and a Haitian father. Bouillon moved to Quebec with his mother when he was only 3 years old. He played Junior hockey in the Quebec Junior Hockey League with the Laval Titans and the Granby Predateurs.

Francis made his professional debut the 1996-97 season in the ECHL with the Wheeling Nailers and played the following season in the IHL with the Quebec Rafales before he was signed as a free agent to an NHL contract by the Montreal Canadiens in 1998.

He played the next 11 seasons, the majority of his career (except for a short stint with the Predators in 2002–03 within the Canadiens organization. At 5'8" and 201 lbs, Bouillon is considered small for an NHL defencemen but is never one to shy away from physical play. According to Pierre Houde, he is one of the strongest players in the NHL, according to official physical tests.