259 Aletheia is a very large main-belt asteroid. It is composed of primitive carbonaceous materials and is very dark in colour, darker than coal.
It was discovered by C. H. F. Peters on June 28, 1886, in Clinton, New York.
It is named after the Greek goddess Aletheia.
Richard P. Binzel and Schelte Bus further added to the knowledge about this asteroid in a lightwave survey published in 2003. This project was known as Small Main-belt Asteroid Spectroscopic Survey, Phase II or SMASSII, which built on a previous survey of the main-belt asteroids. The visible-wavelength (0.435-0.925 micrometre) spectra data was gathered between August 1993 and March 1999.
Lightcurve data has also been recorded by observers at the Antelope Hill Observatory, which has been designated as an official observatory by the Minor Planet Center.