Hardy has shone for Leicester this season and is the Premier League’s top goalscorer with nine strikes.
The 28-year-old has also broken into Roy Hodgson’s England team, earning four caps.
But while Vardy has hinted he could leave Leicester, Ranieri insists he is going nowhere.
The Italian even compared the striker to Barcelona and Brazil superstar Neymar - who has been linked with a move to Manchester United.
"We don't sell Vardy,” Ranieri said. “He's very happy here. Nobody goes in January. Not him, not Riyad [Mahrez], not [Jeffrey] Schlupp.
"It's too early to talk about Vardy along with Neymar. I hope he can improve. If he can continue it'll be fantastic."
“What he is doing is fantastic and I hope he can continue, but it’s important that he doesn’t think about the goals, but that when he comes off the pitch he is happy with his performance.”
Hardy has suggested he could consider his future at Leicester next summer, believing he has repaid his non-league record transfer fee of £1million in 2012, joining from Fleetwood Town.
“It was a big gamble, hopefully, I repaid it all,” said Vardy, who signed a new four-year contract in August 2014.
Ranieri says Vardy deserves England place [AMBIENT]
“I was sad to see him [Nigel Pearson] go but that is football nowadays, that is what happens.
“Managers come and go, but so do players.
"I'm contracted to the club and I'm happy at Leicester. It's all about knuckling down and seeing where we can finish this season.”