In American football, a nickel defense (also known as a 4–2–5 or 3–3–5) is any defensive alignment that uses five defensive backs, of whom the fifth is known as a nickelback.

The nickel defense is a basic defensive formation that is designed to stop a pass play. The alignment features four down lineman, two linebackers, and five defensive backs. It can also be referred to as a nickel play, nickel package or nickel alignment. Also, it is known as a 4–2–5 or 3–3–5 defense.

The nickel defense contains 5 defensive backs on the field at once. The term nickel refers to American currency, which is equal to 5 cents. Nickel defenses are used on 3rd downs when the defense expects the offense to throw the football.

The nickel defense is a solid base defense that is designed to prevent pass completions without giving up too much on the ground. Ideally, it is used in a blitz against slow-developing plays, such as play actions. When coverage holds up, this formation will suffocate the quarterback and force an errant throw or even a sack.

This is a defensive formation used in football, mainly on known passing downs, where the defense brings in an extra defensive back for a total of five. The common formation of players in a nickel defense is four defensive lineman, two linebackers and five defensive backs.