The Lancia Thesis is a full-size car produced by Italian automaker Lancia between 2001 and 2009. It was available with naturally aspirated and turbocharged engines ranging between 2.0 and 3.2 litres in both straight-5 or V6 configurations. Its appearance was based on the 1998 Lancia Diàlogos concept car. The production car premiered at the 2001 Geneva Motor Show and its interior was displayed for the first time at the Frankfurt Motor Show that same year. Sales started in June 2002 in Italy, with export markets following shortly after.

Lancia is an Italian car manufacturer and a subsidiary of Stellantis Europe, which is currently a Stellantis division. The present legal entity of Lancia was formed in January 2007 when its corporate parent reorganised its businesses, but its history is traced back to Lancia & C., a manufacturing concern founded in 1906 in Torino by Vincenzo Lancia (1881–1937) and Claudio Fogolin. It became part of Fiat in 1969.