In the game of baseball, the official scorer is a person appointed by the league to record the events on the field, and to send the official scoring record of the game back to the league offices. In addition to recording the events on the field such as the outcome of each plate appearance and the circumstances of any baserunner's advance around the bases, the official scorer is also charged with making judgment calls that do not affect the progress or outcome of the game. Judgment calls are primarily made about errors, unearned runs, fielder's choice, the value of hits in certain situations, and wild pitches, all of which are included in the record compiled. This record is used to compile statistics for each player and team. A box score is a summary of the official scorer's game record.

In baseball, a stolen base occurs when a runner advances to a base unaided by other actions and the official scorer rules that the advance should be credited to the action of the runner. The umpires determine whether the runner is safe or out at the next base, but the official scorer rules on the question of credit or blame for the advance under Rule 10 of the MLB's Official Rules.