259 Aletheia is a very large main-belt asteroid that was discovered by German–American astronomer Christian Peters on June 28, 1886, at Litchfield Observatory, Clinton, New York.

The dark and heterogeneously composed X-type (Tholen: CP-type) asteroid contains primitive carbonaceous materials, responsible for its low albedo of 0.04.

Aletheia measures about 185 kilometers in diameter and belongs to the largest asteroids of the main-belt.

[1] Richard P. Binzel and Schelte Bus further added to the knowledge about this asteroid in a lightwave survey published in 2003.

[8] It is named after the Greek goddess of truth, Aletheia, the daughter of Zeus and one of the nurses of Apollo.