A chase gun (or chaser), usually distinguished as bow chaser and stern chaser, was a cannon mounted in the bow (aiming forward) or stern (aiming backward) of a sailing ship. They were used to attempt to slow down an enemy ship either chasing (pursuing) or being chased, when the ship's broadside could not be brought to bear. Typically, the chasers were used to attempt to damage the rigging and thereby cause the target to lose performance.
Bow chasers could be regular guns brought up from the gundeck and aimed through specially cut-out ports on either side of the bowsprit, or dedicated weapons made with an unusually long bore and a relatively light ball, and mounted in the bow. Stern chasers could also be improvised, or left permanently in the cabins at the stern, covered up and used as part of the furniture.