The service between Paris and Munich (with some services terminating in Stuttgart) is operated on the high-speed TGV line, with a total journey time of less than four hours to Stuttgart, and less than six hours to Munich. Much of the TGV service has been recently redecorated/rejuvinated to provide comfortable and clean interiors for your journey.
It is also possible to reach Munich via Cologne, or on the City Night Line service, which also calls at Stuttgart.

