Blackfin pupfish (Cyprinodon beltrani) is a species of fish in the family Cyprinodontidae. This pupfish is endemic to Lake Chichancanab in Quintana Roo, Mexico. In almost all places, different Cyprinodon species do not overlap in their range, but there are two notable exceptions and one of these is Lake Chichancanab, which is inhabited by C. beltrani, , C. labiosus, C. maya, C. simus, and C. verecundus (the other place where several Cyprinodon species live together are lakes in San Salvador Island, the Bahamas). Among the endemic Cyprinodon species in Lake Chichancanab, only C. beltrani and C. labiosus still occur in some numbers in their habitat, while the remaining are virtually—if not fully—extinct in the wild (at least some of these still survive in captivity). This species feeds on d