The Seelisberg Tunnel is a motorway tunnel in Switzerland, and forms part of the A2 motorway from Basel to Chiasso.
The tunnel is around 9 km long.
It lies in the southeastern part of the Lake of Lucerne.
After the St. Gotthard, this is Switzerland's second-longest road tunnel. It takes number one nationwide in length only if recognised as a tunnel with split traffic (traffic to Chiasso in one hole, and traffic to Basel in another one).
Proponents for a second Gotthard Road Tunnel hole refer to the Seelisberg Tunnel, which they claim, due to split traffic, results in not only smoother traffic, but blocked traffic only on one side in the case of an accident inside the tunnel.