A Cell on Wheels, usually referred to as a "COW", is a mobile cell site that consists of a cellular antenna tower and electronic radio equipment on a truck or trailer, designed to be part of a cellular network.

COWs are used to provide expanded cellular network coverage and/or capacity at: special events such as major sporting events (Super Bowl, World Series, Rose Bowl, etc.), major conventions, etc.; or in disaster areas where cellular coverage either was never present (e.g. in a wilderness area where firefighters have set up a command center during a major forest fire) or was knocked out by the disaster (e.g. in the Gulf Coast after Hurricane Katrina).

Related to a COW is a CIAB (Cell-in-a-Box). Like COWs, CIABs provide temporary service with temporary equipment. The main difference is that a CIAB is typically placed for a longer period of time than a COW.