The Lithgow Underbridge is a heritage-listed railway underbridge that carries the Main West Line over James Street, in Lithgow, in the City of Lithgow local government area of New South Wales, Australia. The bridge is located approximately 156 kilometres (97 mi) from Central railway station. The bridge was designed by John Whitton as the Engineer-in-Chief for Railways and was built in 1869 by contractor, P. Higgins. It is also known as Lithgow Underbridge. The property is owned by Transport Asset Holding Entity, an agency of the Government of New South Wales. It was added to the New South Wales State Heritage Register on 30 August 2013.

The Main Western Railway is a major railway in New South Wales, Australia. It runs through the Blue Mountains, and Central West regions. It is 825 kilometres (513 mi) long, of which 484 kilometres (301 mi) is currently operational.