Thiess Pty Ltd is an international mining services company based in Brisbane, Australia.

[5] Following restructuring within CIMIC in 2014 and the merger of several international Leighton businesses into Thiess, the company claims to have become the largest contract mining services provider in the world.

Initially the business focused on road-building and earth moving but subsequently expanded into dam construction, open cut mining and other forms of civil engineering.

[18][19][20] In April 1981, the construction division was sold to a consortium of Hochtief (50%), Westfield Group (25%) and Leslie Thiess (25%).

[27] In 2021, CIMIC agreed to joint ownership (50/50) of Thiess with Elliott Advisors.