Cougal Spiral, Heritage railway tunnel in Border Ranges, Australia.

The Cougal Spiral is a tunnel complex along the North Coast railway line in the Border Ranges. It consists of three concrete tunnels of varying lengths that allow trains to navigate steeply rising mountainous terrain.

The Kyogle–South Brisbane extension of the North Coast line opened on 29 August 1930, crossing the NSW–Queensland border beneath Richmond Gap. To hold a ruling grade of 1 in 66, engineers wrapped the single track around a hill, gaining 30 metres without forward progress. The Cougal to Border Loop section was listed on the NSW State Heritage Register on 2 April 1999.

The spiral is one of only two railway spirals in New South Wales, and the whole Cougal-to-Border-Tunnel section was listed on the State Heritage Register on 2 April 1999. Its nickname, Border Loop, has caused confusion in descriptions, since the loop proper is the spiral hill while the state border lies further north in the summit tunnel. The line opened on 29 August 1930.

The spiral and its two short curved tunnels are easily seen from parts of the Lions Road, which crosses the Border Ranges near Richmond Gap. The line runs between 871 and 876 km from Sydney Central, and the whole heritage section extends from Cougal north to the 1,160 m Border Tunnel under the state border. Expect steep, uneven ground off the road.

Trains pass directly over the lower tunnel section while climbing the spiral, creating a double-level railway configuration in the mountainous area. This two-level arrangement was an innovative solution for the steeply rising terrain.