In baseball and softball, an uncaught third strike occurs when the catcher fails to cleanly catch a pitch for the third strike of a plate appearance. In Major League Baseball (MLB), the specific rules concerning the uncaught third strike are addressed in Rules 5.05 and 5.09 of the Official Baseball Rules:

In baseball, an out occurs when the umpire rules a batter or baserunner out. When a batter or runner is out, they lose their ability to score a run and must return to the dugout until their next turn at bat. When three outs are recorded in a half-inning, the batting team's turn expires.