138 Tolosa is a brightly coloured, stony background asteroid from the inner region of the asteroid belt. It was discovered by French astronomer Henri Joseph Perrotin on 19 May 1874, and named by the Latin and Occitan name ( and ) of the French city of Toulouse.
This object is orbiting the Sun at a distance of with an eccentricity of 0.16 and an orbital period of 3.83 years. Its orbital plane is inclined at an angle of 3.2ð relative to the plane of the ecliptic. Measurements of its diameter range from . It is spinning with a rotation period of 10.1 hours.
The spectrum of this asteroid rules out the presence of ordinary chondrites, while leaning in favor of clinopyroxene phases. As of 2006, there are no known meteorites with compositions similar to the spectrum of 138 Tolosa.