100th Regiment

100th Regiment or 100th Infantry Regiment may refer to:


 * 100th Regiment of Foot (disambiguation), several units of the British Army
 * 100th Anti-Tank Regiment, Royal Artillery (The Gordon Highlanders)
 * 100th Heavy Anti-Aircraft Regiment, Royal Artillery
 * 100th Guards Fighter Aviation Regiment
 * 100th Independent Shipborne Fighter Aviation Regiment

Union Army (American Civil War):
 * 100th Illinois Infantry Regiment
 * 100th Indiana Infantry Regiment
 * 100th New York Volunteer Infantry
 * 100th Ohio Infantry
 * 100th Pennsylvania Infantry Regiment