U3 is a line on the Berlin U-Bahn created in its current version on 12 December 2004. The routing is the same as the previous U2 until 1993, only run from Krumme Lanke to Wittenbergplatz.
Until 1993U3 referred to the section of line between Wittenbergplatz and Uhlandstraße. It was renumbered to U15 and became a branch of the U1.
U3 is also the provisional number for a planned new line which would extend the old U3 westwards along Kurfürstendamm towards Westkreuz and eastwards via Potsdamer Platz and Alexanderplatz towards Weißensee. In preparation for this some short sections of tunnel have been built, including a complete station at Potsdamer Platz. However financial constraints mean it is unlikely the line will be constructed in the foreseeable future.