The Lithgow Zig Zag is a heritage-listed former zig zag railway line built near Lithgow on the Great Western Line of New South Wales in Australia. The zig zag line operated between 1869 and 1910, to overcome an otherwise insurmountable climb and descent on the western side of the Blue Mountains. It was designed by John Whitton and built from 1863 to 1869 by Patrick Higgins as contractor. It is also known as the Great Zig Zag Railway and Reserves and Zig Zag Railway. The property is owned by Department of Planning and Infrastructure (State Government). It was added to the New South Wales State Heritage Register on 2 April 1999.