The "Bellerophon" class was equipped with ten breech-loading (BL) Mk X guns in five 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. The secondary, or anti-torpedo boat armament, comprised 16 BL Mk VII guns in single mounts. Two of these guns were each installed on the roofs of the fore and aft centreline turrets and the wing turrets in unshielded mounts, and the other eight were positioned in the superstructure. The ships were also fitted with three 18-inch (450 mm) torpedo tubes, one on each broadside and the third in the stern.