45th Regiment

45th Regiment or 45th Infantry Regiment may refer to:


 * 45th Detached Reconnaissance Regiment, a special forces unit of the Russian Army
 * 45th (Leeds Rifles) Royal Tank Regiment, a unit of the British Army
 * 45th Light Anti-Aircraft Regiment, Royal Artillery, a unit of the British Army
 * 45th Garrison Regiment, Royal Artillery, a unit of the British Army
 * 45th (Nottinghamshire) Regiment of Foot, a unit of the British Army
 * 45th Infantry Regiment (United States), a unit of the United States Army


 * American Civil War regiments :


 * Union (Northern) Army regiments
 * 45th Illinois Volunteer Infantry Regiment
 * 45th Iowa Volunteer Infantry Regiment
 * 45th New York Volunteer Infantry Regiment
 * 45th Wisconsin Volunteer Infantry Regiment