A cornerback (CB) is a member of the defensive backfield or secondary in gridiron football.[1] Cornerbacks cover receivers most of the time, but also blitz and defend against such offensive running plays as sweeps and reverses. They create turnovers through hard tackles, interceptions, and deflecting forward passes.

Other members of the defensive backfield include strong and free safeties.

The cornerback position requires speed, agility, and strength. A cornerback's skill set typically requires proficiency in anticipating the quarterback, backpedaling, executing single and zone coverage, disrupting pass routes, block shedding, and tackling. Cornerbacks are among the fastest players on the field.