The Lake Line[4] (German: Seelinie), as it is referred to by the SBB in English, is the Swiss railway line running from Rorschach via Romanshorn, Konstanz (Germany), Kreuzlingen, Steckborn, Stein am Rhein and Diessenhofen to Schaffhausen.

The scenic route follows the southern border of Lake Constance (Bodensee) and the High Rhine (Hochrhein).

They introduced half-hourly fixed-interval services and modernised both track and rolling stock.

In 1893, the line was connected to the Thur Valley Railway so that trains could operate between Winterthur and Rorschach without reversing direction in Romanshorn.

As of the December 2023 timetable change,[update] sections of the Lake Line are operated by the following regional train services, of which most belong to the Bodensee S-Bahn: The section between Kreuzlingen and Konstanz is also used by InterRegio service of Swiss Federal Railways (SBB).