FIAT 521 was a Automobile manufactured by the Italian Constructeur FIAT between 1929 and 1931.

Replacing the FIAT 520 of 1927, the FIAT 521 was presented in the form of an increased version of its devancière. Longer, with a more important footing, been driven by a six-cylinder motor of 2516 Cm3 developing 50 HP, it was car FIAT the most produced abroad, in particular in Germany, in the factory FIAT-NSU of Heilbronn.

More than 20.000 specimens were built in Italy.

It will be replaced by FIAT 522.