123rd Regiment may refer to:
123rd Regiment of Foot (disambiguation), British regiments 123rd Aviation Regiment, United States 123rd Field Artillery Regiment, United States 123rd Infantry Regiment (United States) 123rd Infantry Regiment "Chieti", Italy 123rd Light Anti-Aircraft Regiment, Royal Artillery 123rd Outram's Rifles, British Indian Army
American Civil War regiments 123rd Illinois Infantry Regiment 123rd Indiana Infantry Regiment 123rd New York Infantry Regiment 123rd Ohio Infantry Regiment 123rd Pennsylvania Infantry Regiment
See also 123rd Brigade (disambiguation) 123rd Division (disambiguation) 123rd (disambiguation)