Ext, ext or EXT may refer to:

• Ext functor, used in the mathematical field of homological algebra
• Ext (JavaScript library), a programming library used to build interactive web applications
• Exeter Airport (IATA airport code), in Devon, England
• Exeter St Thomas railway station (station code), in Exeter, England
• Extended file system, a file system created for Linux
• Exton station (Pennsylvania) (Amtrak station code), in Exton, Pennsylvania
• Extremaduran language (ISO language code), spoken in Spain
• Extremeroller, a former roller coaster at Worlds of Fun, Kansas City, Missouri
• Cadillac Escalade EXT, a sport utility truck