ALS may refer to:

• Acetolactate synthase, an enzyme involved in amino acid biosynthesis
• Albany Law School, a private law school in Albany, New York, United States
• Alexander Language Schools International
• Als, a Danish island in the Baltic Sea
• Amyotrophic lateral syndrom, also known as Lou Gehrig's disease
• Advanced Life Support, a protocol for cardiopulmonary resuscitation
• Advanced Light Source, a synchrotron radiation source at Lawrence Berkeley National Laboratory in California
• Anti-Lag System, an engine control program used on race cars to eliminate turbo lag
• Anterolateral system, a nerve pathway mainly signaling pain and temperature
• Approach lighting system, a lighting system installed on the approach end of an airport runway
• Audio Lossless Coding, part of the MPEG-4 standard for audio/video compression
• Airman Leadership School, the first-level professional military education program for United States Air Force enlisted members
• Alliance for the Liberation of Somalia
• ALS, San Luis Valley Regional Airport's IATA airport code
• Autographed Letter Signed
• als, the ISO 639-3 code for Tosk Albanian
• Automated library system or integrated library system
• Automatic Laser Shutdown
• Alternate line service, a GSM feature for supporting two different phone numbers on the same mobile device.
• Singapore Area Licensing Scheme