Castlereagh Highway is a 790-kilometre (490 mi) state highway located in New South Wales and Queensland, Australia. From north to south the highway traverses South West Queensland and the North West Slopes, Orana, and Central West regions of New South Wales.

South West Queensland is a remote region in the Australian state of Queensland which covers 319,808 km2 (123,479 sq mi). The region lies to the south of Central West Queensland and west of the Darling Downs and includes the Maranoa district and parts of the Channel Country. The area is noted for its cattle grazing, cotton farming, opal mining and oil and gas deposits.