5259 Epeigeus /ɪˈpiːdʒiːəs/ is a mid-sized Jupiter trojan from the Greek camp, approximately 44 kilometers (27 miles) in diameter. It was discovered on 30 January 1989, by American astronomer couple Carolyn and Eugene Shoemaker at the Palomar Observatory in California.^[1] The D-type asteroid has a rotation period of 18.4 hours.^[9] It was named after the Myrmidon hero Epeigeus from Greek mythology.^[1]

Epeigeus is a dark Jovian asteroid in a 1:1 orbital resonance with Jupiter. It is located in the leading Greek camp at the Gas Giant's L₄ Lagrangian point, 60° ahead on its orbit (see Trojans in astronomy).^[3] It is also a non-family asteroid of the Jovian background population.^[4]

It orbits the Sun at a distance of 4.8–5.6 AU once every 11 years and 10 months (4,332 days; semi-major axis of 5.2 AU). Its orbit has an eccentricity of 0.07 and an inclination of 16° with respect to the ecliptic.^[2]

The body's observation arc begins with a precovery taken at the Siding Spring Observatory in March 1980, almost 8 years prior to its official discovery observation at Palomar.^[1]

In the SDSS-based taxonomy, Epeigeus is a D-type asteroid.^[11] It has also been characterized as a D-type by Pan-STARRS' survey.^[9][10] It is the most common spectral type among the Jupiter trojans.

This minor planet was named from Greek mythology after the Greek warrior Epeigeus, who belonged to the Myrmidons commanded by Achilles. He was killed by Hector, who hit him upon the crest of his helmet with a great stone.^[1] The official naming citation was published by the Minor Planet Center on 12 July 1995 (M.P.C. 25443).^[12]