Abstract: An improved apparatus for illuminating keyholes comprised of an annular top housing made of rigid material, having recessed and through holes, and a recessed oval pocket having within two through holes. Top housing (12) is slidably over an annular bottom housing (30) made of the same material as top housing (12), also having recessed and through holes. A printed circuit board (40) having transistor (52), resistor (54), and male power connector (64), mounted and soldered directly on its surface, is housed and affixed within top housing (12), by screw (46), plastic spacer (44), and nut (48). A photoresistor (56) is housed within a pocket (20) and located on top housing (12), its two leads are inserted through two holes (22), located within pocket (20), and soldered directly to printed circuit board (40). A light emitting diode (58), positioned a predetermined distance below a keyhole, and having its two leads soldered to printed circuit board (40), is also housed within top housing (12).