Kepler-16b (formally Kepler-16 (AB)-b) is a Saturn-mass exoplanet consisting of half gas and half rock and ice. It orbits a binary star, Kepler-16, with a period of 229 days. It is the first confirmed, unambiguous example of a circumbinary planet – a planet orbiting not one, but two stars.

Discovered by Laurance Doyle on 15 September 2011 using the transit method during the Kepler Mission, Kepler-16b's presence was detected through the dimming of one of the system's stars. The discovery team reported that the precision in calculating the sizes and masses of the objects in the Kepler-16 system was among the best for any known exoplanet. Kepler-16b ceased transiting the dimmer star in 2014 and stopped crossing the brighter star in 2018. It will remain undetectable by the transit method until around 2042. In 2021, it became the first circumbinary planet detected by the radial velocity method.

Kepler-16b is a gas giant with a radius of 0.77 RJ and a mass of approximately 0.333 MJ. It has a temperature of around 188 K (−85 °C; −121 °F).

Kepler-16b orbits a binary star system consisting of a K-type and an M-type star, which have masses of 0.68 M☉ and 0.20 M☉, respectively. The stars have surface temperatures of 4450 K and 3311 K and orbit each other about every 41 days.

Kepler-16b orbits its parent stars every 228 days at a distance of approximately 0.704 AU. Its small eccentricity remains unexplained, and it is thought to have migrated from elsewhere in the system.

Kepler-16b lies near the outer edge of the habitable zone, with its orbit at about 104 million kilometers from the binary system. While the chances of life on the gas giant itself are remote, simulations suggest the possibility of an Earth-sized moon captured by Kepler-16b.

The discovery team initially denoted it as Kepler-16 (AB)-b. Informally, it has been referred to as "Tatooine," a reference to the fictional planet from the Star Wars series due to its orbit around two stars.