ACAS

ACAS may refer to:

In aviation:

• Airborne Collision Avoidance System, an International Civil Aviation Organization standard
• Assistant Chief of the Air Staff, a senior appointment in the Royal Air Force

In other fields:

• Aboriginal Children's Advancement Society, an organization in New South Wales
• Acas (Advisory, Conciliation and Arbitration Service), an independent non-departmental public body of the Government of the United Kingdom
• Acâş, a commune in Satu Mare County, Romania
• Allianz Common Applications and Services GmbH, Germany, a subsidiary of Allianz
• Associate in the Casualty Actuarial Society, a level of membership in the Casualty Actuarial Society
• Assured Compliance Assessment Solution, security compliance assessment for network attached systems
• Australian Collaboration for Accelerator Science, based at the Australian Synchrotron, Victoria