The Bugatti 18/3 Chiron is a 1999 concept car developed by French automobile manufacturer Bugatti Automobiles and designed by Fabrizio Giugiaro of Italdesign. Powered by a 6.3 L W18 engine, it is a 2-seater mid-engine coupé. The 18/3 Chiron was the last in a trio of Bugatti concept cars by Italdesign, after the 1998 EB 118 coupé and the 1999 EB 218 saloon.

Italdesign Giugiaro S.p.A. is a design and engineering company and brand based in Moncalieri, Italy, that traces its roots to the 1968 foundation of Studi Italiani Realizzazione Prototipi S.p.A. by Giorgetto Giugiaro and Aldo Mantovani. Best known for its automobile design work, Italdesign also offers product design, project management, styling, packaging, engineering, modeling, prototyping and testing services to manufacturers worldwide. As of 2010, Italdesign employs 800 people.