Overview
A foul ball is a batted ball that the rules treat as belonging to foul territory. Whether a ball is foul is not decided by whether it passed outside the foul lines in the air; it is decided by where the ball settles, where it first falls, where a fielder or an umpire touches it, and on which side of first or third base it passed. A batted ball that settles in foul territory between home and first or between home and third, one that first falls in foul territory beyond first or third base, one that bounds past first or third base over foul territory, and one that touches a player, an umpire or an object that does not belong on the ground while over foul territory are all foul. A fly ball is judged by the relative position of the ball and the foul line, not by whether the fielder stood in fair or foul territory when touching it. One point deserves emphasis: the foul lines and the foul poles count as fair territory. A ball that strikes the pole is not foul, and a drive that clips the outfield pole and lands in the stands is a home run.
Two strikes and three exceptions
The foul ball rule is one of baseball's distinctive features: fouls count as strikes when the batter has zero or one strike, but once the count reaches two strikes, additional fouls do not advance the count. The phrase 'infinite fouls after two strikes' captures how much room a batter has to battle, yet the rulebook carves out exceptions. First, a batter who bunts foul on the third strike is out on strikes. Second, a ball that goes sharp and direct from the bat into the catcher's mitt and is legally caught is a foul tip, which counts as a strike, so with two strikes it ends the at-bat as a strikeout; if the catcher fails to hold it, it is an ordinary foul. Third, a fly ball into foul territory that a fielder catches puts the batter out on the spot. An ordinary foul that nobody catches also makes the ball dead, so runners must return to their bases, whereas a legally caught foul tip leaves the ball in play and runners may keep going. In other words, the fouls a batter can keep hitting without limit are the ones he produces with his own swing and that nobody catches.
Tactical value and spectator safety
Fouls carry significant tactical value beyond being mere mishits. The ability to foul off borderline pitches with two strikes, wearing down the pitcher's count while waiting for a hittable offering, is a prized professional skill. For pitchers, extended foul-ball at-bats mean rising pitch counts and accelerated fatigue, potentially forcing an early exit. Because bunting the ball away is not an option once the batter has two strikes, however, he has to do it with his own swing. Foul balls also raise spectator safety concerns. Injuries from batted balls entering the stands have prompted action worldwide, and Japanese ballparks have widened protective netting and barriers as venues have been renovated or expanded (as of 2026). Whether fans may keep foul balls varies by venue; most Japanese stadiums permit it.