S21 (Berlin)

S21
S21 route
Overview
Line number6017 Westhafen–Hbf–Potsdamer Platz
6019 Wedding–Hauptbahnhof
Technical
Track gauge1435
Electrification800 V Third rail DC
Route map

Berlin Ringbahn
(Northern circular)
Westhafen
Wedding
Perleberger Brücke
Phase I
Phase II
Reichstag
(cancelled)
Potsdamer Platz
Phase II
Phase III
Gleisdreieck
Yorckstraße
Julius-Leber-Brücke
Berlin Ringbahn
(Southern circular)
Südkreuz
Berlin Ringbahn
(Southern circular)

S21 or City S-Bahn is a project to build a second north-south route for the Berlin S-Bahn. The new route will parallel the Nord-Süd Tunnel and connect Berlin Hauptbahnhof to the Berlin Ringbahn, both to the north and south. The first section is under construction and is expected to go into operation on March 30, 2026; the line that will operate on the newly opened route will initially be designated S15. Further extensions are still in the planning phase.