12-pounder gun or 12-pdr, usually denotes a gun which fired a projectile of approximately 12 pounds.

Guns of this type include:

• 12-pounder long gun, the naval muzzle-loader of the Age of Sail
• Canon de 12 de Vallière, French cannon of 1732
• Canon de 12 Gribeauval, French field cannon of the mid-late 18th century
• Canon lourd de 12 Gribeauval, French heavy cannon of the mid-late 18th century
• Canon obusier de 12, French 12-pounder cannon-howitzer of 1853. Known in the US as "12 pounder Napoleon"
• M1841 12-pounder howitzer, American howitzer having the same caliber (4.62 inches) as a 12-pounder field gun
• One of the Dahlgren guns of the American Civil War
• Ordnance BL 12 pounder 7 cwt, British field gun, 1885–1892
• Ordnance QF 12 pounder 8 cwt, British naval landing gun, late 19th century and early 20th century
• Ordnance BL 12 pounder 6 cwt, British light field gun, 1894–1916
• QF 12 pounder 12 cwt naval gun, British "Long 12" of 1890s–1940s
• QF 12 pounder 12 cwt AA gun, British AA gun of World War I
• QF 12 pounder 18 cwt naval gun, British naval gun of 1904–1920s
• RBL 12 pounder 8 cwt Armstrong gun, British field gun of 1859
• Twelve-pound cannon, cannon sized for a 12-pound ball, see Naval artillery in the Age of Sail
• 12-pounder Whitworth rifle, British rifled breechloader field gun of 1860s
• Erroneously, the QF 3 inch 20 cwt gun