Part of the south of the county may also be merged into a new Sligo-Leitrim constituency.
It means the next set of TDs to represent the county – five instead of six – will have a vast geographical area to cover.
The cutting of a TD from Donegal is part of a recommendation that eight TDs be cut from current numbers to reflect population changes.
The commission accepted submissions from interested parties, including TDs, in addition to census data, in arriving at its decisions.
The five-person commission is chaired by High Court judge Mr Justice John Cooke. The other four members are: clerk of the Dáil Kieran Coughlan; clerk of the Seanad Deirdre Lane; Ombudsman Emily O’Reilly; and secretary general of the Department of the Environment Geraldine Tallon.