S9 is a line on the Berlin S-Bahn.

[1] It operates from Flughafen BER to Spandau through Berlin Hauptbahnhof (Berlin Central Station) over: The S9 was created on 2 June 1991, replacing the Blue route of the S3 between Charlottenburg and Flughafen Berlin Schönefeld (now Schönefeld (bei Berlin) station), with the western terminus extended by one stop to Westkreuz.

[2][3]