Amid reports the 26-year-old could be allowed to leave the Stadio San Paolo at the end of the season, the outspoken president insisted that is not the case.
Premier League duo Chelsea and Manchester United have been linked with Hamsik, who has seen high-profile team-mates such as Ezequiel Lavezzi and Edinson Cavani leave in recent seasons, both to Paris Saint-Germain.
De Laurentiis told Radio Kiss Kiss. "It's only journalists who put him on the market.
"Marek has to come and tell me if he wants to go, but there is no more Neapolitan player than him. He has become Neapolitan and for me he is absolutely not for sale.
"Of course if he came to me and asked to leave, then we'd have to discuss it."
De Laurentiis also confirmed he was considering a follow-up move for Lyon midfielder Maxime Gonalons, after seeing a €17 million bid in January fail.
"We will have time to think about it," he said. "I found an immediate agreement with Gonalons, but it was (Lyon president Jean-Michel) Aulas who dug his heels in and pushed things beyond every level.
"Now I don't want to take revenge on Lyon, as that is not part of my nature. Everyone thinks they have gems and ask for outlandish prices."
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