A sealing ring for a spark plug that has an external thread for screwing into an internal combustion engine, a collar and a thread undercut between the external thread and the collar. The sealing ring includes a ring-shaped solid sealing element made from metal. The sealing element has two planar annular sealing surfaces that are arranged parallel to one another. An annular retaining element composed of an elastomer for engaging in the thread undercut of the spark plug in a self-retaining manner is attached to the sealing element on the inner ring side thereof. Also included is a spark plug comprising such a sealing ring, and an internal combustion engine comprising such spark plugs.