Notholebias is a genus of small annual killifish in the family Rivulidae, native to coastal Brazil. As with other annual killifish, its species inhabit temporary pools that dry out seasonally; the adults do not survive the dry period, and the population persists as eggs buried in damp substrate that enter diapause and hatch once the rains refill the pools. The atlas covers 2 species, Notholebias cruzi and N. minimus, both very small fish at roughly 1–1.5 in - among the smallest killifish kept by specialists.
These are specialist fish rather than mainstream aquarium stock, kept mostly by dedicated killifish hobbyists willing to manage the peat-based annual breeding cycle that species in this group require. Conservation status is a real concern: one species in the genus is Endangered and the other has not yet been formally assessed, and both are flagged in the atlas's CARES conservation-priority list, reflecting how exposed small, short-lived seasonal-pool populations are to habitat loss along Brazil's developed coastline.