NSU-Fiat was a German automobile manufacturer which produced Fiat vehicles under license at a plant acquired from NSU in Heilbronn from 1929 to 1957, and between 1957 and 1971 as Neckar Automobilwerke AG.

[1] The 1929 deal left two businesses producing petrol driven vehicles with similar names located barely 7 kilometers (4 miles) apart: the two were frequently confused with one other.

"NSU Automobil-AG" was a subsidiary of Fiat, manufacturing Fiat passenger cars carrying a "NSU-Fiat" badge and located in Heilbronn, while NSU Werke AG in nearby Neckarsulm produced motor-bikes, becoming during the 1950s one of the largest motor-bike manufacturers in the world.

(The same Fiat-designed models were also produced under license in Nanterre, France by SIMCA-Fiat the cars subsequently becoming known simply as "Simcas".)

Arguments centred on what had been agreed about rights to the "NSU" name and, in particular, whether an arguably informal letter dated 5 January 1929 on the subject had long-standing contractual force.

[1] The judge decided that the 1929 letter could not have the contractual force necessary to bind the parties over use of the "NSU" name, because of a danger that its effect, if valid, would be to damage marketplace competition and thereby run counter to the public interest.