239 Adrastea is a main belt asteroid. It was discovered by Johann Palisa on 18 August 1884 in Vienna, and was named after the Greek nymph Adrasteia. This asteroid is orbiting the Sun at a distance of with a period of and an eccentricity (ovalness) of 0.23. The orbital plane is tilted at an angle of 6.17ð to the plane of the ecliptic.
Photometric data collected during 2009 were used for light curve analysis of this asteroid, yielding a rotation period of with a brightness variation of in magnitude. The result is close to the period from a study performed in 2003. The asteroid is roughly 42 km in diameter.