ALS may refer to:
- Als, a Danish island in the Baltic Sea
- Amyotrophic lateral sclerosis, also known as Lou Gehrig's disease or Maladie de Charcot
- 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 professional military education 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
- Alternate line service, a GSM feature for supporting two different phone numbers on the same mobile device.
