A boom barrier, also known as a boom gate, is a bar, or pole pivoted to allow the boom to block vehicular access through a controlled point. Typically the tip of a boom gate rises in a vertical arc to a near vertical position.

Boom gates are typically found at level (rail) crossings, drawbridges, parking facilities, checkpoints and entrances to restricted areas. They are also the usual method for controlling passage through toll booths, and can also be found on some freeway entrance ramps which are automatically controlled to drop to restrict traffic in the event of accident cleanup or road closures without the need to dispatch road workers or law enforcement to use a vehicle to block the way.

Some boom gates are automatic and powered, others are manually operated. Manual gates are sometimes hung in the manner of a normal gate (i.e.hinged horizontally). In some places, boom gates are installed across suburban streets as a traffic calming measure, preventing through traffic, while allowing authorisedvehicles such as emergency services and buses to take advantage of the shorter and more direct route.