31st Brigade or 31st Infantry Brigade may refer to:
Australia 31st Brigade (Australia)
Germany 31st Airborne Brigade (Bundeswehr)
France 31st Brigade (France)
Greece 31st Mechanized Infantry Brigade (Greece)
India 31st Indian Brigade of the British Indian Army in the First World War 31st Indian Infantry Brigade of the British Indian Army in the Second World War
Italy 31st Armored Brigade "Curtatone"
Malaysia 31st Infantry Brigade (Malaysia)
Russia 31st Guards Air Assault Brigade
Sovet Union 31st Mechanized Brigade (Soviet Union)
Ukraine 31st Mechanized Brigade (Ukraine) 31st Public Order Brigade (Ukraine)
United Kingdom 31st Armoured Brigade (United Kingdom) 31st Infantry Brigade (United Kingdom) 31st (North Midland) Anti-Aircraft Brigade 31st Brigade, Royal Field Artillery
United States 31st Air Defense Artillery Brigade (United States) 31st Chemical Brigade
See also 31st Division (disambiguation) 31st Group (disambiguation) 31st Regiment (disambiguation) 31st Battalion (disambiguation) 31st Squadron (disambiguation)