Heidelberg-Altstadt station (also known as Karlstorbahnhof—"Karlstor station") is a station on the eastern edge of the old town of Heidelberg, Baden-Württemberg, Germany. Until 13 December 2008, the station was called Heidelberg Karlstor.

The original station building was built on the Neckar Valley Railway (Neckartalbahn) in 1872 and 1873 at Karlstor ("Charles’ Gate"), a gate at the eastern end of the old town (Altstadt). The present station building is the result of a reconstruction between 1934 and 1936. The building is a heritage-listed building.

In the meantime, it has been used as a municipal office building and, since 1995, it has housed the Kulturzentrum Karlstorbahnhof (“Karlstor station cultural centre”), which was established by Mayor Beate Weber. With a wide range of theatrical performances, concerts, readings and exhibitions and smaller festivals, it forms a significant part of the Heidelberg cultural landscape.

Since 2004, the station has been a stop on the Rhine-Neckar S-Bahn network and a new platform was built near the former station building for it. The station was given its present name, Heidelberg-Altstadt at the 2008/2009 timetable change on 14 December 2008.

Line	Route	Frequency
S1	Homburg (Saar) – Kaiserslautern – Neustadt (Weinstr) – Ludwigshafen (Rhein) – Mannheim – Heidelberg Hbf – Heidelberg-Altstadt – Eberbach – Mosbach (Baden) – Osterburken	Hourly
S2	Kaiserslautern – Neustadt (Weinstr) – Ludwigshafen (Rhein) – Mannheim – Heidelberg Hbf – Heidelberg-Altstadt – Eberbach – Mosbach (Baden)	Hourly
S5	Heidelberg Hbf – Heidelberg-Altstadt – Neckargemünd – Meckesheim – Sinsheim (Elsenz) – Eppingen	Hourly
S51	Heidelberg Hbf – Heidelberg-Altstadt – Neckargemünd – Meckesheim – Neckarbischofsheim Nord – Aglasterhausen	Hourly

The station is served by several local bus routes.

• Kulturzentrum Karlstorbahnhof