Safety (S) is a position in American and Canadian football, played by a member of the defense. The safeties are defensive backs who line up from ten to fifteen yards behind the line of scrimmage. There are two variations of the position in a typical formation, the free safety (FS) and the strong safety (SS). Their duties depend on the defensive scheme. The defensive responsibilities of the safety and cornerback usually involve pass coverage towards the middle and sidelines of the field, respectively.

Safeties are the last line of defense, and are thus expected to be sure tacklers. As professional and college football have become more focused on the passing game, safeties have become more involved in covering the eligible pass receivers.

The strong safety, sometimes in college called a rover (ROV), tends to be somewhat larger and stronger than the free safety. However, the word strong is used because he is assigned to cover the "strong side" of the offense, the side on which the big, powerful tight end lines up on offensive plays. The strong safety tends to play closer to the line and assist in stopping the run. He may also be responsible for covering a player, such as a running back or fullback or H-back, who comes out of the backfield to receive a pass. A strong safety's duties are a hybrid of those belonging to a linebacker and those of the other defensive backs, in that he both covers the pass and stops the run. Three of the most notable strong safeties are Ken Houston, John Lynch and Rodney Harrison. Among the best active strong safeties are Troy Polamalu, Adrian Wilson, Patrick Chung, and Eric Berry.