This subseries documents Fiat, which was built by S.A. Fabbrica Italiana di Automobili of Turin, Italy (1899-1906); S.A. Fabbrica Italiana did Automobili Torino of Turin, Italy (1906-1943); FIAT Società per Azioni of Turin, Italy (1943-1978); and Fiat Auto S.p.A. (1979-Present).

Founded in 1899 by a group of investors that included Giovanni Agnelli, Fiat was originally a manufacturer of high-priced automobiles. Agnelli gained majority control of the firm 1907 and he shifted the company's focus to the low-priced sector, a move which soon resulted in Fiat becoming Italy's largest automaker. In 1945, the Agnelli family was removed from its leadership role in Fiat by the National Liberation Committee because of the firm's connections to the recently overthrown government of Benito Mussolini. But the Agnelli family regained its leadership of Fiat when Gianni Agnelli became general manager of Fiat in 1963.

Fiat is presently Europe's fourth largest automaker and has operations all over the world. Over the course of its history, it gained control of a number of other Italian automakers, including Lancia (1968), Ferrari (1969), Alfa Romeo (1986), and Maserati (1993). From 1950 to 1982, Fiat also owned an interest in Seat. In the 2011, Fiat became the majority shareholder of Chrysler. See also Alfa Romeo, Chrysler, Ferrari, Lancia, Maserati, and Seat.

This subseries has been divided into four sub-subseries: