The Zurich –Affoltern am Albis –Zug railway is a railway connecting the Swiss cities of Zurich and Zug via Affoltern am Albis. It was opened by the Zurich–Zug–Lucerne Railway (German: Zürich-Zug-Luzern-Bahn) on 1 June 1864. The Zug–Lucerne line was opened by the same company on the same day. The line officially begins in Zürich Altstetten, which was still an independent municipality at that time. The line's only significant traffic consists of services on Zurich S-Bahn line S5. Long distance trains between Zurich, Zug and Lucerne now run via the Zimmerberg Base Tunnel, the Thalwil–Arth-Goldau line and the Zug–Lucerne line.