(79983) 1999 DF9

' (provisional designation ') is a trans-Neptunian object of the Kuiper belt, classified as a non-resonant cubewano, that measures approximately 270 kilometers in diameter.

Discovery
It was discovered on 20 February 1999, by American and British astronomers Jane Luu, Chad Trujillo and David C. Jewitt at the U.S. Kitt Peak National Observatory in Arizona. As no precoveries were taken, the minor planet's observation arc begins with its discovery observation in 1999.

Classification and orbit
The minor planet is a classical Kuiper belt object or "cubewano", which are not in an orbital resonance with Neptune and do not cross the giant planet's orbit. It orbits the Sun at a distance of 39.8–53.6 AU once every 319 years and 1 month (116,560 days). Its orbit has an eccentricity of 0.15 and an inclination of 10° with respect to the ecliptic. This makes it a relatively eccentric body for a classical Kuiper belt object, which typically have low-eccentricities of 0.10 or less.

Physical characteristics
In February 2001, a rotational lightcurve was published for this minor planet from photometric observations by Portuguese astronomer Pedro Lacerda and the discovering astronomer Jane Luu. Lightcurve analysis gave a relatively short rotation period of $6.65$ hours with a brightness variation of 0.40 magnitude (U=2).

The Collaborative Asteroid Lightcurve Link assumes a low albedo of 0.10 and calculates a mean-diameter of 265 kilometers, based on an absolute magnitude of 6.0, while the Johnston's archive give a diameter of 306 kilometers for an albedo of 0.09. Due to its small size, it is unlikely to be classified as a dwarf planet.

Numbering and naming
This minor planet was numbered by the Minor Planet Center on 4 May 2004. As of 2018, it has not been named.