Bavarian B IIIs were steam locomotives of the Royal Bavarian State Railways (Königlich Bayerische Staatsbahn). Eight examples were delivered by Maffei in 1852; the remainder came from Hartmann. The machines by Hartmann had great similarity to those of the Class A IV, which were manufactured at the same time. Unlike the Hartmann engines, these locomotives also had a steam dome. This was later added to the Hartmann variants. All the engines had a Crampton boiler with smooth tubes and a Kirchweger condenser. They were equipped with a 3 T 5 tender.