Tinia is the only known moon of the trans-Neptunian object 55637 Uni.
Tinia was discovered in August 2005, by observations with the Hubble Space Telescope, and announced on 22 February 2007. It was named together with Uni on 1 September 2025 after Tinia, the Etruscan sky god and husband of the Etruscan goddess of love and fertility Uni.
Tinia was discovered at 0.16 arcseconds from Uni with a difference in absolute magnitude of 2.5 Its diameter is estimated at . Assuming an albedo similar to its primary, Tinia should have a diameter of approximately 190 km; assuming an albedo of 0.05, typical of cool classical KBOs of similar size, it should have a diameter of approximately 260 km.
Tinia completes one complete orbit around Uni every days, at a distance of , indicating a total system mass of . Its orbital eccentricity is .