CSAS may refer to:
- Canadian Special Air Service Company, a post-war parachute unit
- Center for the Study of the American South
- Central sleep apnea syndrome
- Combined Statistical Area, a statistical unit used by the United States Census and other offices
- Coal Smoke Abatement Society, a predecessor to Environmental Protection UK
- Community Safety Accreditation Scheme
- Chattanooga School for the Arts & Sciences
- Czechoslovak Academy of Sciences
- Command Stability Augmentation System, a fly-by-wire feature of the Panavia Tornado