100th Regiment or 100th Infantry Regiment may refer to:
Union Army (American Civil War) 100th Illinois Infantry Regiment 100th Indiana Infantry Regiment 100th New York Infantry Regiment 100th Ohio Infantry Regiment 100th Pennsylvania Infantry Regiment 100th United States Colored Infantry Regiment
Other uses 100th Regiment of Foot (disambiguation), several units of the British Army 100th Anti-Tank Regiment, Royal Artillery (The Gordon Highlanders) 100th (Yeomanry) Regiment Royal Artillery 100th Heavy Anti-Aircraft Regiment, Royal Artillery 100th Light Anti-Aircraft Regiment, Royal Artillery 100th Guards Fighter Aviation Regiment 100th Independent Shipborne Fighter Aviation Regiment 100th Regiment Winnipeg Grenadiers
See also 100th Brigade (disambiguation) 100th Division (disambiguation)