Bethungra Spiral, Heritage-listed rail spiral in Bethungra, New South Wales, Australia

The Bethungra Spiral is a heritage-listed rail spiral on the Main Southern line between Junee and Cootamundra, carrying the northbound track of the Sydney–Melbourne corridor. The up track diverges from the original 1878 line, passes under it through a tunnel, then spirals around a hill through a second tunnel, crossing over itself before a viaduct returns it to the left side of the down track.

The structure was built during the 1940s to replace the original single-track line from 1878. This redesign became necessary to handle heavier train loads and reduce the need for helper locomotives on the steep gradient.

The Epping Model Railway Club, based in Epping, New South Wales, built a demountable HO scale model of the spiral measuring about 5 by 3 metres. It is occasionally shown as a fully operational exhibit at appropriate functions.

From the Olympic Highway, a sign on the right marks the turnoff to the Rail Spiral Lookout and Bethungra Dam; an all-vehicle dirt road leads about 3 km to a parking area and interpretive signboard. A substantial viewing platform nearby shows a Sydney-bound train emerging from the tunnel and, two minutes later, crossing over that same tunnel. Other spots on the road reveal three tracks at three heights on the hillside east of the highway.

The structure uses two tunnels allowing the northbound track to pass underneath the original line and then curve back over itself at a higher elevation. This clever engineering solution lets the track gain the necessary altitude while crossing the historic route.