The BL 6-inch Mk XXII gun[note 1] was a British high-velocity 6-inch 50-calibre wire-wound naval guns deployed on the Nelson-class battleships from the 1920s to 1945.

They were originally designed as secondary armament for the proposed G3 class battlecruisers.

When the G3 class were cancelled after the Washington Naval Treaty the guns and mountings were later used as secondary armament on the two Nelson-class battleships, serving throughout World War II.

The Mk VIII gun mountings could elevate from +60 degrees to -5 degrees, while the telescopic power rammers for the gun loaded at a +5-degree fixed angle.

[2] Although classified as a dual-purpose gun and capable of high-angle fire, their training and elevation speeds were too slow for the anti-aircraft role and their main use was against surface targets.