121st Brigade may refer to:
China 121st Brigade, Republic of China; see January 28 incident order of battle
India 121 (Independent) Infantry Brigade, part of 8th Infantry Division (India)
Soviet Union 121st Guards Artillery Brigade 121st High-Power Howitzer Artillery Brigade, part of 5th Shock Army 121st Separate Tank Brigade, part of 65th Army (Soviet Union)
Ukraine 121st Territorial Defense Brigade
United Kingdom 121st Brigade (United Kingdom) 121st Brigade, Royal Field Artillery
See also 121st Division (disambiguation) 121st Regiment (disambiguation) 121st Battalion (disambiguation)