In American and Canadian football, a line of scrimmage is an imaginary transverse line (across the width of the football field) beyond which a team cannot cross until the next play has begun. Its location is based on the spot where the ball is placed after the end of the most recent play and following the assessment of any penalty yards.

A line of scrimmage is parallel to the goal lines and touches one edge of the ball where it sits on the ground prior to the snap. Under NFL, NCAA, and NFHS rules, there are actually two lines of scrimmage at the outset of each play: one that restricts the offense and one that restricts the defense. The area between the two lines (representing the length of the ball as extended to both sidelines) is called the neutral zone. Only the center, the offensive player who snaps the ball, is allowed to have any part of his body in the neutral zone. In order for there to be a legal beginning of a play, a certain number of the players on the offensive team, including certain eligible receivers, must be at, on or within a few inches off their line of scrimmage.