Lieutenant General Sir Iven Giffard Mackay (7 April 1882 – 30 September 1966) was a senior Australian soldier who served in both World Wars. A graduate of the University of Sydney, Mackay taught physics there from 1910 until 1914, when he joined the Australian Imperial Force. He served with the 4th Infantry Battalion at Gallipoli, where he distinguished himself in hand-to-hand fighting at the Battle of Lone Pine. In April 1916, he assumed command of the 4th Infantry Battalion on the Western Front and led it at the Battle of Pozieres, Battle of Bullecourt and Battle of Broodseinde. He was promoted to brigadier general in June 1918, and led the 1st Infantry Brigade at the Battle of Hazebrouck, the Battle of Amiens and in the attack on the Hindenburg Line.