Reports from Papua New Guinea say the first candidate has registered to contest elections for the Bougainville provincial seat in the national parliament.
The National newspaper reports Isaiah Moroko had paid the nomination fee at the Electoral Commission office in Buka.
An official said Mr Moroko was contesting as an independent candidate, but was being supported by the president of the autonomous provincial government, Joseph Kabui.
The by-election is being held after the former Bougainville MP and provincial governor, John Momis, resigned to stand against Mr Kabui for the presidency in the autonomous provincial government.
Officials believe up to six candidates, one of them a woman, may contest the election.