45th Regiment

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


 * 45th Rattray's Sikhs, a unit of the British Indian 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) (Sherwood Foresters) Regiment of Foot, a unit of the British Army
 * 45th Cavalry (India), a unit of the Indian Army
 * 45th Infantry Regiment (Imperial Japanese Army)
 * 45th Detached Reconnaissance Regiment, a special forces unit of the Russian Army
 * 45th Infantry Regiment (United States), a unit of the United States Army

Union Army regiments

 * 45th Illinois Volunteer Infantry Regiment
 * 45th Iowa Volunteer Infantry Regiment
 * 45th New York Volunteer Infantry Regiment
 * 45th Wisconsin Volunteer Infantry Regiment
 * 45th Ohio Infantry
 * 45th Regiment Kentucky Volunteer Mounted Infantry
 * 45th Regiment Massachusetts Volunteer Infantry
 * 45th United States Colored Infantry Regiment

Confederate Army regiments

 * 45th Arkansas Infantry (Mounted)
 * 45th North Carolina Infantry
 * 45th Tennessee Infantry Regiment
 * 45th Virginia Infantry