209 Dido is a main-belt asteroid with a diameter of 179±1 km. It was discovered by C. H. F. Peters on October 22, 1879, in Clinton, New York. The asteroid was named after the mythical Carthaginian queen Dido. This object is orbiting the Sun at a distance of 3.15 AU with an eccentricity (ovalness) of 0.058 and a period of 5.59 yr. The orbital plane is tilted at an angle of 7.2° to the plane of the ecliptic.