An intraoral illumination device for illuminating the interior of the mouth of a dental patient. The device comprises a flexible container having container defining walls, a portion of the walls being light transmitting. The device is sized for insertion into the mouth and placement against an interior surface of the mouth, e.g., the gum. A pressure-sensitive adhesive layer covers a portion of the walls for adhesively mounting the device to the interior surface of the mouth. A first chamber and a second chamber are within the container. The chambers are connected to each other by a frangible wall. Each of the chambers contain a chemical composition that when mixed together create a chemiluminescent reaction that produces light. When the frangible wall is fractured by flexing the container, it permits the compositions to mix within the container to create a chemiluminescent reaction that emits light through the container walls to illuminate the mouth, permitting dental procedures to be easily performed.