51st Regiment

51st Regiment or 51st Infantry Regiment may refer to:


 * 51st Regiment of Foot (disambiguation), several units of the British Army
 * 51st Highland Volunteers, a unit of the British Army
 * 51st Infantry Regiment (United States)
 * 51st Armoured Regiment (India)
 * 51st Coast Artillery Regiment, a unit of the United States Army
 * 51st (Leeds Rifles) Royal Tank Regiment
 * 51st (Highland) Searchlight Regiment, Royal Artillery
 * 51st (London) Heavy Anti-Aircraft Regiment, Royal Artillery
 * 51st (Westmoreland and Cumberland Yeomanry) Field Regiment, Royal Artillery
 * 51st Sikhs (Frontier Force), a unit of the British Indian Army

Union Army (American Civil War):
 * 51st Illinois Infantry Regiment
 * 51st Indiana Infantry Regiment
 * 51st Regiment Massachusetts Volunteer Infantry
 * 51st New York Volunteer Infantry
 * 51st Ohio Infantry
 * 51st Pennsylvania Infantry Regiment
 * 51st Wisconsin Volunteer Infantry Regiment
 * 51st United States Colored Infantry Regiment