121st Brigade

121st Brigade may refer to:
 * 121st Brigade a 'bantam' infantry formation of the British Army 1915–18
 * 121st Infantry Brigade a deception formation of the British Army in Sicily 1943–44
 * CXXI Brigade Royal Artillery a British Army unit 1915–16
 * 121st Artillery Brigade of the former Soviet Ground Forces
 * 121st Brigade of the Chinese Republican army 1932
 * 121st Field Artillery Brigade of the Egyptian Army
 * 121st (Independent) Infantry Brigade of the Indian Army
 * 121st Tank Brigade of the Red Army 1942
 * 121st High-Power Howitzer Artillery Brigade of the Red Army 1945
 * 121st Territorial Defense Brigade (Ukraine), a unit of the Ukrainian Territorial Defense Forces