The German term Donnerbüchse (plural: Donnerbüchsen, formerly Donnerwagen) means "thunderbox" and is the nickname for the four-wheeled, open, passenger coaches, built from 1921 onwards, that served with the Deutsche Reichsbahn.

In the early days, they were also called Ackermann'sche Donnerbüchse ("Ackermann's thunderboxes") after the departmental head responsible for them in the Ministry of Transport.

In addition to the passenger coaches, 917 Pwi luggage vans also appeared between 1923 and 1931 to a similar design.

In 1951 several Ci coaches were converted into driving trailers (CPwif) for shuttle services headed by steam locomotives.

At the beginning of the 1960s the retirement of the Donnerbüchsen began; however many were converted to works coaches (Bauzugwagen) and used as such.