Siata (Società Italiana Auto Trasformazioni Accessori in English Italian Car Transformation Accessories Company) was an Italian car tuning shop and manufacturer founded in 1926 by amateur race car driver Giorgio Ambrosini.

Siata initially sold performance parts to modify and tune cars manufactured by Fiat. After World War II, the company began making its own sports cars under the Siata brand until its eventual bankruptcy following the first Arab oil embargo in the mid-1970s.