Robert Ivan Lucas (born 7 June 1953) is an Australian former politician and a former member of the South Australian Legislative Council between the 1982 election and the 2022 election, representing the South Australian Division of the Liberal Party of Australia.

Lucas served as the Treasurer of South Australia between 2018 and 2022 in the Marshall government, and previously served in the role between 1997 and 2002 in the Olsen and Kerin governments.

During this time (2002 to 2007), Lucas was the Leader of the Opposition in the Legislative Council.

In 2014 Lucas returned to the Treasury portfolio albeit as Shadow Treasurer following the retirement of the previous portfolio holder and former Liberal leader Iain Evans.

[4] Lucas's mother Yoshiko was a "war bride"[5] who met his father, Bob, who was part of the British Commonwealth Occupation Force in Japan.