The blackfin cisco (Coregonus nigripinnis) was a North American salmonid fish in the freshwater whitefish sub-family Coregoninae.

This silvery, deep-bodied fish with black fins, large eyes, a blunt snout and a terminal mouth, was one of the largest forms of ciscoes.

The decline of the species was largely caused by overfishing, which occurred during the 1950s as the result of mismanagement in an unregulated fishery, and predation from the invading sea lamprey.

The introduced alewife (Alosa pseudoharengus) and rainbow smelt (Osmerus mordax) were also aggressive predators of juveniles.

Current threats to any remaining populations include commercial fishing, predation by rainbow smelt and interbreeding with lake herring (Coregonus artedi).