A defensive strategy in baseball in which one or more players in the outfield or the infield change their positioning in order to maximize defensive efficiency against a batter's hitting tendencies or to adapt to a specific in-game situation.
There are many different shifts that take place throughout the course of a baseball game. For instance, in a situation where the defense expects a bunt play, they will "bring the corners in", meaning that the first and third baseman both move closer to the plate in order to field the ball as quickly as possible if it is hit in their direction. In another example, outfielders may shift their position in if there is a runner at third-base, so they have a better chance of throwing the player out at home plate.
Some radical shifts in defensive positioning can occur when teams are facing specific hitters, such as moving more players than usual to one side of the field if the batter has a tendency to pull the ball to one side of the field. This positioning is also known as the "overshift" and was first used as a strategy against Ted Williams in 1946.