40th Regiment

40th Regiment, 40th Infantry Regiment or 40th Armoured Regiment may refer to:


 * Infantry regiments :
 * 40th (2nd Somersetshire) Regiment of Foot, a unit of the United Kingdom Army
 * 40th Infantry Regiment (United States), a unit of the American Regular Army.


 * Armoured regiments :
 * 40th (The King's) Royal Tank Regiment, a unit of the United Kingdom Army
 * 40th/41st Royal Tank Regiment, a unit of the United Kingdom Army


 * Artillery regiments :
 * 40th Regiment Royal Artillery, a unit of the United Kingdom Army


 * Aviation regiments :
 * 40th Fighter Aviation Regiment, a unit of the Yugoslav Air Force


 * Communications regiments :
 * 40 (Ulster) Signal Regiment, a unit of the United Kingdom Army


 * American Civil War regiments :
 * 40th Illinois Volunteer Infantry Regiment, a unit of the Union (Northern) Army during the American Civil War
 * 40th Iowa Volunteer Infantry Regiment, a unit of the Union (Northern) Army during the American Civil War
 * 40th Wisconsin Volunteer Infantry Regiment, a unit of the Union (Northern) Army during the American Civil War
 * 40th New York Volunteer Infantry Regiment, a unit of the Union (Northern) Army during the American Civil War