88 Thisbe is the 13th largest main-belt asteroid. C. H. F. Peters discovered it on 15 June 1866, named after Thisbe, heroine of a Roman fable. This asteroid orbits the Sun at a distance of over a period of and an orbital eccentricity (ovalness) of 0.165. The orbital plane is inclined at an angle of 5.219° to the ecliptic.
On 7 October 1981, asteroid 88 Thisbe was observed to occult the 9th-magnitude star SAO 187124 from 12 sites. The timing of the different chords across the asteroid provided a diameter estimate of . This is 10% larger than the diameter estimate based on radiometric techniques. During 2000, 88 Thisbe was observed by radar from the Arecibo Observatory. The return signal matched an effective diameter of 207 ± 22 km. This is consistent with the asteroid dimensions computed through other means. But Iris is strongly perturbed by many minor planets such as 10 Hygiea and 15 Eunomia. In 2011, Baer revised this to 18.3 kg with an uncertainty of 1.1 kg.
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