Leptopanchax is a genus of small fish, up to 5 cm (2.0 in) long, in the family Rivulidae. They are found in southeastern Brazil from Paraná to Rio de Janeiro. Depending on the exact species, they inhabit small seasonal channels in the Atlantic rainforest or temporary pools in open habitats. Several Leptopanchax species are very rare and L. sanguineus is possibly extinct.