In American football, a back is a player who plays off of the line of scrimmage (as opposed to a lineman). Historically, the term "back" was used to describe multiple positions on offense and defense, although more descriptive and specific position naming is now common. Back also was a sole position in the one-platoon system era.

Thus, "back" can refer to positions including:^[1]

• Fullback, one of the two rushing positions, along with the halfback
• Halfback, one of the two rushing positions, along with the fullback
  • Tailback, a halfback who is lined up deep in the backfield, as in the I formation
• H-back, an offensive position that lines up similarly to a tight end, but is set back from the line of scrimmage
• Quarterback, a member of the offensive team that lines up directly behind the offensive line and receives the snap of the ball at the beginning of a play
• Running back, a member of the offensive backfield whose primary role is to receive handoffs from the quarterback to run with the ball
  • Singleback, an offensive formation that only requires one running back
• Slotback, a wide receiver on the offensive team that is positioned in the "slot" (located between the last offensive lineman/tight end and the next wide receiver)
• Upback, a blocker who lines up behind the line of scrimmage in punting situations
• Wingback, a position in the single wing formation, usually a running back

• Defensive back, a member of the defensive team who take positions somewhat back from the line of scrimmage
  • Cornerback, a member of the defensive team that primary defends wide receivers
  • Dimeback, a cornerback or safety who serves as the sixth defensive back
  • Nickelback, a cornerback or safety who serves as the additional defensive back in a nickel defense
  • Safety, although this position does not have "back" word in it, the safety is a defensive back player. In Canadian football, the safeties are known as "defensive halfback".
• Linebacker, a member of the defensive team that is positioned approximately three to five yards behind the line of scrimmage

• History of American football positions
• Back (disambiguation)