Baiomys, the New World pygmy mice, is a genus of rodents in the family Cricetidae. Together with Scotinomys, it forms the tribe Baiomyini. It contains the smallest rodents in North America. It currently contains three extant species:

• Southern pygmy mouse, Baiomys brunneus
• Mexican pygmy mouse, Baiomys musculus
• Northern pygmy mouse, Baiomys taylori

Additionally, there are seven known fossil species:

• Baiomys aquilonius Zakrzewski, 1969
• Baiomys brachygnathus (Gidley, 1922)
• Baiomys intermedius Packard & T. Alvarez, 1965
• Baiomys kolbi Hibbard, 1952
• Baiomys minimus (Gidley, 1922)
• Baiomys rexroadi Hibbard, 1941
• Baiomys sawrockensis Hibbard, 1953

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