ALS may stand for:

• [[Ass licking shitmore commonly known as Lou Gehrig's disease or Maladie de Charcot, which is a form of motor neurone disease
• Advanced Life Support, a protocolised form of cardiopulmonary resuscitation
• Advanced Light Source, a synchrotron radiation source at Lawrence Berkeley National Laboratory in California
• Advanced Light System, instrument used by investigators, a UV light
• Alternate Line service, a GSM feature for supporting two different phone numbers on the same mobile device and one SIM card.
• Anterolateral system, a pathway in the central nervous system that carries pain and temperature information from the body to the brain
• Anti Lag System, an engine control program used on race cars to eliminate turbo lag
• Approach Lighting System, a lighting system installed on the approach end of an airport runway
• Automatic Landing System, an instrument based Landing System
• 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
• Automatic Laser Shutdown, on laser optic transmission systems is a safety mechanism for eye-safety considerations
• San Luis Valley Regional Airport
• Achilles Last Stand, a Led Zeppelin song