A by-election was held for the Australian House of Representatives seat of Kalgoorlie on 18 December 1920.

It was triggered by the expulsion from the House of Labor Party MP Hugh Mahon.

The subsequent by-election was won by Nationalist Party candidate George Foley.

After the death of the Irish nationalist Terence McSwiney, as the result of a hunger strike in October 1920, Mahon attacked British policy in Ireland, and the British Empire as a whole, at an open-air meeting in Melbourne on 7 November, referring to it as "this bloody and accursed despotism".

Subsequently, Prime Minister Billy Hughes moved to expel him from the House of Representatives.