The Bavarian Class D X engines were saturated steam locomotives of the Royal Bavarian State Railways (Königlich Bayerische Staatsbahn).
The locomotives, which were built by Krauss were similar to the Class D VIII, but were smaller and lighter.
The first engine was only 8,880 mm long due to the lack of a coal bunker on the driver's cab.
All the vehicles were taken over by the Deutsche Reichsbahn-Gesellschaft in 1925 as DRG Class 98.77 and remained in service until 1931.
Only numbers 98 7706 and 98 7707 were retired shortly after the renumbering.