The goalkeeper (sometimes termed goaltender, netminder, GK, goalie or keeper) in many team sports which involve scoring goals, is a designated player charged with directly preventing the opposing team from scoring by blocking or intercepting opposing shots on goal. Such positions exist in bandy, rink bandy, camogie, association football, Gaelic football, international rules football, floorball, handball, hurling, field hockey, ice hockey, roller hockey, lacrosse, ringette, rinkball, water polo, and shinty as well as in other sports.

In most sports which involve scoring in a net, rules apply to the goalkeeper that do not apply to other players. These rules are often instituted to protect the goalkeeper (being a target for dangerous or even violent actions). This is most apparent in sports such as ice hockey and lacrosse, where goalkeepers are required to wear special equipment like heavy pads and a face mask to protect their bodies from the impact of the playing object (e.g. ball or puck.)

In some sports, goalkeepers may have the same rights as other players; in association football, for example, the keeper is allowed to kick the ball just as any other player, but may also use their hands to handle the ball in a restricted area. In other sports, goalkeepers may be limited in the actions they are allowed to take or the area of the field or rink where they may be; in the NHL, for example, goalkeepers may not play the puck in the restricted areas behind the net or take the puck across the red line.