The Lainz Tunnel is a 12.8-kilometre-long, double-track railway tunnel in Vienna. It forms one part of a wider tunnel network that includes the neighbouring Wienerwald Tunnel, it connects Austria's Western, Southern, Eastern and Donauländebahn railways and greatly simplifies international and national connectivity in Vienna. The Lainz Tunnel has been in service since 9 December 2012.

The Wienerwald Tunnel is a 13.35 km (8.30 mi) long railway tunnel near Vienna, passing underneath the northern part of Wienerwald. It is part of a 250-kilometre-per-hour (160 mph) section between Vienna and St. Pölten which is part of Austria's Western Railway.