The Zürich–Winterthur railway is Switzerland's busiest railway line. Opened in 1855, it runs from Zürich Hauptbahnhof to Winterthur via several routes. It is a bottleneck in Swiss rail transport. Practically all lines of the core network of the Zürich S-Bahn use parts of this line.

Zürich Hauptbahnhof is the largest railway station in Switzerland and one of the busiest in Europe. Zürich is a major railway hub, with services to and from across Switzerland and neighbouring countries such as Germany, Italy, Austria and France. The station was originally constructed as the terminus of the Spanisch Brötli Bahn, the first railway built completely within Switzerland. Serving up to 2,915 trains per day, Zürich HB is one of the busiest railway stations in the world. It was ranked as the second-best European railway station in 2020.