In baseball, a fair ball is a batted ball that has not yet become a foul ball, and that...

• settles on fair ground between home and first base, or between home and third base, or
• is on or over fair territory when bounding to the outfield past first or third base, or
• touches first, second, or third base, or
• touches the person of an umpire or player while the ball is on or over fair ground, or
• passes out of the playing field in flight while over fair ground.

It is possible for a ball moving in foul territory to become a fair ball. Batted balls can also be foul balls or foul tips.

On a fair ball, the ball is alive; runners may attempt to advance and fielders may try to record outs. A batted ball is presumed to be fair until it is ruled a foul ball or a foul tip.