85 Io (eye'-oh) is a large and dark-colored Main belt asteroid. It is probably a primitive body composed of carbonates.

Like 70 Panopaea it orbits within the Eunomia asteroid family but it is most likely not related to the shattered parent body.

It was discovered by C. H. F. Peters on September 19, 1865 and named after Io, a lover of Zeus in Greek mythology.

A diameter of 178 kilometres was measured from an occultation of a star on December 10, 1995.

Io is also the name of the volcanic satellite of Jupiter.