Fast may refer to:

• Fasting, abstaining from food
• a speed racing for dirt horse racing tracks

FAST may stand for:

• Federation Against Software Theft, a UK organization that pursues those who illegally distribute software
• Firefighter Assist and Search Team, a team of firefighters dedicated the rescue of other firefighters
• Foundation for Advancement of Science and Technology, Pakistan
• Fast Search & Transfer, a Norwegian company focusing on data search technologies
• Fleet Antiterrorism Security Team, a branch of the United States Marine Corps
• Farpoint Asteroid Search Team
• Focused Assessment with Sonography for Trauma, a means of assessment of a trauma patient, usually in the Emergency Department
• Five hundred meter Aperture Spherical Telescope, the world's largest single-dish radio telescope (China)
• Facial Affect Scoring Technique, a system devised to help researchers identify the facial expressions that typically accompany certain emotions
• Fast Auroral Snapshot Explorer, one in the series of NASA's Small Explorer (SMEX) spacecraft designed to study particles and fields in the regions of Earth's atmosphere where electrons form the aurora

See also

• ATSF