172 Baucis is a large main belt asteroid that was discovered by French astronomer Alphonse Borrelly on February 5, 1877, and named after a fictional character in the Greek legend of Baucis and Philemon.

It is classified as an S-type asteroid based upon its spectrum.

Photometric observations of this asteroid from the southern hemisphere during 2003 gave a light curve that indicated a slow synodic rotation period of 27.417 ± 0.013 hours and a brightness variation of 0.25 in magnitude.

[3] Polarimetric study of this asteroid reveals anomalous properties that suggests the regolith consists of a mixture of low and high albedo material.

This may have been caused by fragmentation of an asteroid substrate with the spectral properties of CO3/CV3 carbonaceous chondrites.