In baseball, a save is credited to a pitcher who finishes a game for the winning team under certain prescribed circumstances. Most commonly a pitcher earns a save by entering in the ninth inning of a game in which his team is winning by three or fewer runs and finishing the game by pitching one inning without losing the lead. The number of saves or percentage of save opportunities successfully converted are oft-cited statistics of relief pitchers, particularly those in the closer role. The save statistic was created by journalist Jerome Holtzman in 1959 to "measure the effectiveness of relief pitchers" and was adopted as an official Major League Baseball (MLB) statistic in 1969. The save has been retroactively tabulated for pitchers before that date. Mariano Rivera is MLB's all-time leader in regular-season saves with 652, while Francisco Rodríguez earned the most saves in a single season with 62 in 2008.

In baseball and softball, a relief pitcher or reliever is a pitcher who pitches in the game after the starting pitcher has been removed because of fatigue, ineffectiveness, injury, or ejection, or for other strategic reasons, such as inclement weather delays or pinch hitter substitutions. Relief pitchers are further divided informally into various roles, such as closers, setup men, middle relief pitchers, left/right-handed specialists, and long relievers. Whereas starting pitchers usually throw so many pitches in a single game that they must rest several days before pitching in another, relief pitchers are expected to be more flexible and typically pitch in more games with a shorter time period between pitching appearances but with fewer innings pitched per appearance. A team's staff of relievers is normally referred to metonymically as a team's bullpen, which refers to the area where the relievers sit during games, and where they warm-up prior to entering the game.