Abstract: An antenna adapter may be used for mounting an antenna to a vehicle or other object via the object's antenna mount, making antenna theft more difficult. The adapter is therefore configured to both receive the antenna and engage the antenna mount. The antenna adapter includes one or more elements that are configured to assist in removable engagement of the antenna adapter with the antenna, such as a groove and a set screw that screws through the antenna and into the groove of the adapter. The antenna adapter may also include another element that is configured to maintain the antenna at a particular radial orientation with respect to the antenna adapter when engaged therewith.