An anti-roll bar, known in the US as a sway bar or stablizer bar, is a suspension component which increases the roll stiffness of a vehicle, cutting down on body roll in corners.

Anti-roll bars are torsion bar springs which run across the vehicle and are connected to the suspension arms at each end. When the suspension on both sides rises and falls by the same amount, the whole anti-roll bar turns in its mountings and it has no effect on the suspension movement. But when the suspension rises on one side and falls on the other, which is what happens when the car rolls in a corner, the anti-roll bar is twisted, and this resists the roll motion.

Stiff anti-roll bars can introduce quirks such as reduced ride quality and bump steer on poor road surfaces.

Anti-roll bar is sometimes abbreviated to ARB.