The 15.5 cm/60 3rd Year Type (60口径三年式15.5cm3連装砲, 60 kōkei sannenshiki 15.5 centi sanrensōhō) was a dual-purpose naval gun used by the Imperial Japanese Navy on the Yamato-class battleships as secondary armament in four triple turrets, the Mogami-class cruisers in five triple turrets (later converted to five twin 20 cm/50 3rd Year Type naval gun turrets) and on the light cruiser Ōyodo in two triple turrets. The Tone-class cruisers were also initially planned to carry the 15.5 cm/60 3rd Year Type in five triple turrets, but were redesigned with the 20 cm/50 3rd Year Type in four twin turrets. They were also deployed on 60° single mounts as coastal defense guns in the Tokyo Bay area. Construction was of the monobloc type with autofretting and used a Welin breech block mechanism which could