The BL 10 inch guns Mks I, II, III, IV[3] were British rifled breechloading 32-calibre naval and coast defence guns in service from 1885.

After Mk IV of 1889 the Royal Navy discontinued the 10-inch calibre in favour of 9.2-inch and 12-inch.

Mks II, III and IV guns were interchangeable and equipped the following warships : A 25-ton version with a barrel of 300 inches (30 calibres) and firing a 450-pound projectile was supplied in 1884 to the Australian colony of Victoria, mounted on the gunboat HMVS Victoria.

[6] Mk I was an Elswick Ordnance design used only for coastal defence.

Mks II, III and IV were interchangeable Woolwich Arsenal designs used on warships but also for coastal defense around the British Empire, some on disappearing carriages.