Gary Humphries was a Member of the Legislative Assembly for the Australian Capital Territory from 1989 to 2003, serving in many ministerial roles.  He was Chief Minister from 2000 to 2001.

From 2003 to 2013 he was the Liberal Senator for the ACT.  He held various responsibilities in the Federal Opposition, including Shadow Parliamentary Secretary for Defence Matériel.

After leaving the Senate he was Deputy President of the Administrative Appeals Tribunal until 2021.  He also chaired the Australian Institute of Administrative Law, the Anzac Centenary Public Fund and RSPCA Australia.

He is presently enrolled as an PhD student in the School of History at the Australian National University, writing the history of ACT self-government.