The Boßler Tunnel is a railway tunnel currently under construction as part of the new Wendlingen-Ulm high-speed railway. The tunnel is approximately long, built as two parallel single-track tunnels. The tunnel runs between Aichelberg and Mühlhausen im Täle under the Roter Wasen and the Boßler mountain. It is one of a series of tunnels underneath the Swabian Jura range. When completed, it will be the longest tunnel on the line and the fifth longest tunnel in Germany (after the Landrücken Tunnel, the Münden Tunnel, the Filder Tunnel and the Katzenberg Tunnel).