308 Polyxo is a main-belt asteroid that was discovered by A. Borrelly on 31 March 1891, in Marseilles.

[2] 308 Polyxo is classified as a rare T-type asteroid, with a spectrum that bears some similarity to the Tagish Lake meteorite.

[6] A spectral feature at a wavelength of 3.0 μm suggests aqueous alteration of some surface materials.

[4] Photometric measurements reported in 1983 give a rotation period of 12.03 hours and a brightness variation of 0.20 in magnitude.

The adaptive optics instrument at the W. M. Keck Observatory shows an oblate object with a diameter of 130 km.