221 Eos is a large main-belt asteroid that was discovered by Austrian astronomer Johann Palisa on January 18, 1882, in Vienna.

[5] The asteroid is orbiting the Sun with a semimajor axis of 3.01 AU, a period of 5.22 years, and an eccentricity of 0.1.

Based upon its spectral characteristics, this object is classified as a K-type asteroid.

The orbital properties show it to be a member of the extensive Eos asteroid family, which is named after it.

[6] The spectral properties of the asteroid suggest it may have come from a partially differentiated parent body.