The Hallandsås Tunnel, inaugurated in December 2015, is Sweden's longest railway tunnel. It consists of two parallel single-track tunnels, each 8.7 kilometres long (although Stockholm's metro has a longer tunnel in the form of the Blue Line). The tunnels are part of the expansion of the West Coast Line to increase traffic capacity. The Hallandsås Tunnel runs from Förslöv in the south to Båstad in the north, near the border with Halland.

Planning began in 1975, and construction started in 1992. The hill was completely excavated in 2013. Between 2013 and 2015, railway installations were carried out in the tunnel. The construction has been notable for the technical difficulties encountered, which have caused extensive delays and significant cost overruns for the project.

The breakthrough in the eastern tunnel was made in August 2010, while the western tunnel was pierced in September 2013. Wooden sleepers and rails on the old track over the ridge between Båstad and Förslöv are now being dismantled and removed. Plans are in place for the track bed to become a bicycle path.