The D.341 were part of a post-World War II effort from the Italian state railways FS to replace their steam locomotives on non-electrified lines. They were designed in collaboration with Fiat and Breda and were produced in two series with different engines, depending from the manufacturer. The second series had a slightly different appearance. Two prototypes were also built by Ansaldo and Reggiane.
D.341 has two small cabs, one at each end, separated by a large compartment including the engine, the cooling devices and the transmission. The two engines were both V-12 engines, 12 piston, coupled to a DC 450/700 V generator provided by Magneti Marelli for the FIAT locomotives, and by Breda or Ocren in the others. Power is fed to four electric motors having a maximum power of 177 kW (237 hp) each in the first series, and 192 kW (257 hp) in the second one.