In baseball, base running is the act of running around the bases performed by members of the team at bat. In general, base running is a tactical part of the game with the goal of eventually reaching home to score a run. The goal of batting is generally to produce base runners, or help move base runners along. Runners on second or third base are considered to be in scoring position since a normal hit, even a single, will often score them. Part of the goal of a runner and a batter is to get the runner into scoring position.

The term batter-runner is used in official terminology to identify an offensive player from the time he puts a fair ball into play or the third strike is not caught (thereby ceasing to be a batter) until the end of the play he initiated, whether the play results in the player being put out or becoming a runner by legally attaining first base or any subsequent base. The term is generally not applied if the batter hits a foul ball or to a player awarded first base, e.g., for a base on balls.

For any base running to occur, a batter must initially become a base runner. This happens when:

• he hits a ball into fair territory and is not put out,
• he receives a base on balls,
• he is hit by a pitch,
• he hits into a fielder’s choice,
• the defensive team commits an error that allows him to reach base,
• there is an uncaught third strike, or
• the catcher or any fielder interferes with him, or
• a fielder other than the catcher interferes with him.