A building automation system (BAS) is a system that regulates various electric, electronic, and mechanical devices in a building. It is also known as a building management system or a building control system.

Building automation is just a small part of a much larger picture. Until now, various systems in buildings have been treated as isolated closed blocks with their own interfaces and no contact with other systems. However, building automation is finally beginning to completely incorporate these distinct systems, into the same network, along with other systems such as access control units, fire alarms, elevators, and so on.