The Mazda Demio (マツダ・デミオ, Matsuda Demio) is a subcompact/supermini/B-segment small car manufactured by Mazda since 1996. While sold across four generations in the domestic Japanese market, the Demio nameplate was rarely used outside of Japan, where it was usually called the Mazda2. The Demio nameplate was retired in 2019 as Mazda changed over to "Mazda2" for their home market as well.

The Demio is built on the Mazda D platform and was preceded by two other small cars based on the platform: the Ford Festiva (designed and built by Mazda for Ford and also sold as the Mazda 121) that was introduced in 1986 on the DA platform and the Revue (sold by Mazda's Autozam marque) introduced in 1990 on the DB platform. The Mazda Demio added the DW ("W" for wagon) platform in 1996. The name "Demio" is derived from Latin meus to show possession, which in many Romance languages has become "mio."

The third generation Demio earned the 2008 World Car of the Year title, while the fourth generation was awarded the 2014–2015 "Japanese Car of the Year".

The first generation Demio was sold as the Ford Festiva Mini Wagon in some markets.