The Mazda3 is a compact car manufactured by Mazda. It was first introduced in 2003 as a 2004 model, replacing the Familia/323/Protegé in the C-segment.

Compact car is a vehicle size class—predominantly used in North America—that sits between subcompact cars and mid-size cars. "Small family car" is a British term and a part of the C-segment in the European car classification. However, before the downsizing of the United States car industry in the 1970s and 1980s, larger vehicles with wheelbases up to 110 in (2.79 m) were considered "compact cars" in the United States.