Abstract: A self-closing toilet seat assembly includes a longitudinal hinge tube mounted in a cavity on the underside of a toilet lid in coaxial alignment with the hinge flanges thereof. The hinge tube is secured in hinged engagement with both the toilet lid and seat by means of a pair of slow-close hinge dampeners. A self-closing mechanism, in association with a mounting base attached to the bowl of a conventional toilet and to the underside of the hinge tube, is responsive to manual lifting of either the toilet lid itself or of both the toilet lid and the toilet seat to the open or vertical position for initiating closing rotation of the toilet lid and the toilet seat, if also upright, to the vertical tipping point, past which they continue to gravitationally rotate to the closed position, at a rate limited by the slow-close hinge dampeners.