Juve have been linked with a move for the mercurial Argentina international, with several outlets suggesting that Gonzalo Higuain could move the other way.
Marotta, though, says such talk is nonsense, and has scotched any suggesting that Inter have entered into negotiations with Icardi, who scored 29 goals in 34 Serie A appearances this season.
“Juventus players are considered unsellable, up until the moment they ask to be sold," he told reporters. "In the case of Higuain, even if he’s at the World Cup, we’ve received no such request.
“Icardi is a suggestion. Obviously we’re talking about an excellent player, one who belongs to Inter, and then there are these news reports that we’ve approached him.
“All that falls into the realms of fantasy, fantasy football.”
Juve have confirmed the signing of goalkeeper Mattia Perin this summer, and are also hopeful of completing the acquisition of Emre Can from Liverpool on a free transfer.
“We’re optimistic on Emre Can,” Marotta confirmed.
“We can say that the contact with his representatives has started and are going well. We hope we can reach a conclusion in 10 days.”
Juve won a seventh straight Scudetto in 2017-18, finishing four points ahead of second-placed Napoli.