In American football, blocking or interference involves legal movements in which one player uses his body to obstruct another player's path. The purpose of blocking is to prevent defensive players from tackling the ball carrier, or to protect a quarterback who is attempting to pass, hand off or run the ball. Offensive linemen and fullbacks tend to do the most blocking, although wide receivers are often asked to help block on running plays and halfbacks may be asked to help block on passing plays, while tight ends perform pass blocking and run blocking if they are not running routes to receive passes. Overall, blocking is a skill that virtually every football player may be required to do at some point, even defensive players in the event of a turnover.

American football, also known as gridiron football, is a team sport played by two teams of eleven players on a rectangular field with goalposts at each end. The offense, the team with possession of the oval-shaped football, attempts to advance down the field by running with the ball or throwing it, while the defense, the team without possession of the ball, aims to stop the offense's advance and to take control of the ball for themselves. The offense must advance at least ten yards in four downs or plays; if they fail, they turn over the football to the defense, but if they succeed, they are given a new set of four downs to continue the drive. A game is won by the team with the higher number of points, which are scored primarily by advancing the ball into the opposing team's end zone for a touchdown or kicking the ball through the opponent's goalposts for a field goal.