Senator Andrew Lockhart McLachlan CSC CStJ was elected by a joint sitting of the Parliament of South Australia to serve as a Senator for the State on 6 February 2020. In May 2022, he was elected by the people of South Australia to the Commonwealth Parliament to continue his service as a Senator for South Australia. On 26 July 2022, Senator McLachlan was elected to the position of Deputy President of the Senate and Chair of Committees.

Prior to his service in the Australian Parliament, Andrew was elected to the Legislative Council of the South Australian Parliament on 15 March 2014. He was subsequently elected President of the Legislative Council in May 2018 and served in this role until February 2020.

Andrew has held a commission in the Australian Army Reserve and has seen service in Afghanistan. In 2007 he was awarded the Conspicuous Service Cross for his services to the Army. As a veteran, he continues to serve as a Legatee of Legacy.

He is a volunteer for St John Ambulance Australia and serves as its President of Operations in South Australia. In 2014 he was made a Commander in The Most Venerable Order of the Hospital of Saint John of Jerusalem.