Coregonus nilssoni is a putative species of whitefish, part of the Coregonus lavaretus complex (European whitefish).

[1] It is a pelagic fish feeding on zooplankton.

Its distribution is in lakes of Sweden, southern Norway, Denmark and Poland.

[1] In Sweden, the name C. nilssoni has referred to a form of whitefish known as the planktonsik.

That is however no more considered a distinct species but an ecotype within Coregonus maraena ("Coregonus maraena morphotype nilssoni"), and not different from "Coregonus maraena morphotype megalops".