Odostomia is the most speciose genus of minute sea snails, pyramidellid gastropod mollusks. This genus is placed in the family Pyramidellidae in the subfamily Odostomiinae. There are several hundred species in this diverse genus (Schander et al. 1999)

Most of the description of species in the genus Odostomia was carried out by Dall & Bartsch in 1909. Many of the described species are however suspected of being synonyms, or are proven synonyms.

The genus Odostomia Fleming, 1813 was used by 19th century authors, particularly in the European literature, for most of the smaller Pyramidellidae. It is still a catchall for most small pyramidellids lacking both axial and spiral sculpture. Some authors, e.g. Høisæter (2014), Peñas, Rolán & Swinnen (2014) and Giannuzzi-Savelli et al. (2014) who are here followed have attempted to redistribute some of the species, but there are still many species remaining unduly under Odostomia. For these, the database WoRMS has refrained from making new combinations not backed by (or implicit from) a published source but, unless otherwise noted, the species that were already "accepted" under a subgenus now raised to full genus have been marked as "accepted" under that full genus.

The European and American species of Odostomia differ in several anatomical and shell characteristics. They are therefore likely to be assigned to different genera.

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