The 22-year-old is being linked with a move to Premier League side Chelsea.
“There’s been no contact direct or otherwise with Chelsea for Marek,” Napoli director of sport Riccardo Bigon told Sky Italia.
“Hamsik is untransferable for us, he is in the second year of a five-year plan started by our president.”
Hamsik joined Napoli from Brescia in a £4.8million deal in the summer of 2007.