The S15 is a regional railway line of the S-Bahn Zürich on the Zürcher Verkehrsverbund (ZVV), Zürich transportation network, and is one of the network's lines connecting the cantons of Zürich and St. Gallen.
- S 15 Niederweningen – Hardbrücke – Zürich HB – Uster – Wetzikon – Rapperswil Stops between Stadelhofen and Wetzikon only in Uster.
The line runs from Niederweningen, in the north-west of the canton of Zürich, to Zurich Hauptbahnhof before continuing via Zürich Stadelhofen and Uster to Rapperswil. It serves the following stations:
- Niederweningen Dorf
- Zürich Oerlikon
- Zürich Hardbrücke
- Zürich Hauptbahnhof
- Zürich Stadelhofen
- Rüti ZH
- Jona (SG)
The train frequency on the line is usually 30 minutes and the trip takes 72 minutes.
With the introduction of the new timetable in late 2015, the western terminus of the service was switched from Affoltern am Albis to Niederweningen. The stations between Zürich Altstetten and Affoltern am Albis that are no longer served by the S15 are now served by the S14.