20th Regiment may refer to:
Infantry regiments
20th Infantry Regiment (United States) 20th Regiment of Bengal Native Infantry, an East India Company unit 20th Duke of Cambridge's Own Infantry (Brownlow's Punjabis), a British Indian Army unit 20th Continental Regiment, a Continental Army unit 20th Regiment of Foot, a British Army unit
American Civil War regiments
Union (Northern) regiment
20th Connecticut Infantry Regiment
20th Illinois Infantry Regiment
20th Indiana Infantry Regiment
20th Iowa Volunteer Infantry Regiment
20th Kansas Militia Infantry Regiment
20th Regiment Kentucky Volunteer Infantry
20th Maine Volunteer Infantry Regiment
20th Regiment Massachusetts Volunteer Infantry
20th Michigan Volunteer Infantry Regiment
20th New York Volunteer Infantry Regiment
20th Pennsylvania Infantry
20th Wisconsin Volunteer Infantry Regiment
Confederate (Southern) regiments
20th Arkansas Infantry Regiment
20th Tennessee Infantry Regiment
20th Virginia Infantry
Other regiments
20th Marine Regiment (United States) 20th Field Artillery Regiment, RCA, Royal Canadian Artillery 20th Field Artillery Regiment (United States) 20th Hussars, a cavalry regiment of the British Army 20th Lancers (Pakistan), an armoured regiment 20th Light Dragoons, a cavalry regiment of the British Army 20th Surveillance and Target Acquisition Regiment, Royal Australian Artillery