The Fiat 521 is a passenger car produced by Fiat between 1928 and 1931. The 521 was derived from predecessor model (Fiat 520), it had a bigger engine and chassis. The 521 C was shorter variant of this car. This car was produced outside Italy, most notably at the Fiat-NSU plant in Heilbronn, starting in 1930. This set Fiat on the path to its subsequent multinational status.

More than 33,000 Fiat 521s were produced in Italy and Germany.