An illustrative wireless controller for a lighting fixture includes an actuator module, a control module, and optionally a sensor module. The control module includes a radio, an antenna, a user interface, and a controller. A control housing defines an enclosure for the control module and defines a male fitting for mounting the control housing to an opening defined through the light fixture housing. The actuator module includes an AC-to-DC converter, a power monitoring circuit, a load switching circuit, and a dimming control circuit. An actuator housing defines an enclosure for the actuator module and for mounting the actuator housing inside the fixture housing. The control module receives wireless lighting control signals, decodes the wireless lighting control signals, and controls the actuator module based on at least the decoded wireless lighting control signals, to control the electrical power supplied by a power converter to a lighting fixture lamp.