A device for illuminating a door knob keyhole of a conventional door locking set, the device includes a ring-shaped lighting assembly. The lighting assembly is detachably secured to a face of the door knob of the conventional door locking set. The lighting assembly includes an annular base structure and a light source support, each having a central hole sized large enough to expose the keyhole when the lighting assembly is detachably secured to the door knob. The light source includes a plurality of light-emitting diodes (LEDs) which are retained in the light source support. An electrical circuit, which includes a depressible switch, is provided for activating the LEDs.