Assiminea pecos is a rare species of snail in the family Assimineidae known by the common name Pecos assiminea. It is native to New Mexico and Texas in the United States. Specimens known from Mexico are now treated as members of a separate species, Assiminea cienegensis. The Pecos assiminea was federally listed as an endangered species of the United States in 2005. This snail was first described in 1987. It is generally between 1 and 2 millimeters long. Little is known about its life history.