The Lötschberg is an Alpine mountain massif, usually associated with a major, historically important transit axis of the Alps in Switzerland with, at its core, the Lötschen Pass. The mountain pass, which culminates at nearly 2,700 metres above sea level, are part of the eastern Bernese Alps, whose main crest straddles the border between the cantons of Bern and Valais. The valleys concerned by the Lötschberg are those of the Kander in the Berner Oberland, with Kandersteg at the head of it, and a secluded side-valley of the Upper Valais, the Lötschental, with Ferden at the valley's entrance and at the bottom of the pass.

The Lötschberg Base Tunnel (LBT) is a 34.57 km (21.48 mi) railway base tunnel on the BLS AG's Lötschberg line cutting through the Bernese Alps of Switzerland some 400 m (1,300 ft) below the existing Lötschberg Tunnel. It runs between Frutigen, Bern, and Raron, Valais.