The "Colossus" class was equipped with ten breech-loading (BL) Mark XI guns in five hydraulically powered twin-gun turrets, three along the centreline and the remaining two as wing turrets. The centreline turrets were designated 'A', 'X' and 'Y', from front to rear, and the port and starboard wing turrets were 'P' and 'Q' respectively. Their secondary armament consisted of sixteen BL Mark VII guns. Ten of these were mounted in the forward superstructure and six in the aft superstructure in single mounts. Four 3-pounder () saluting guns were also carried. The ships were equipped with three 21-inch (533 mm) submerged torpedo tubes, one on each broadside and another in the stern, for which 18 torpedoes were provided.