The 22-year-old was subject to a reported £1 million bid from Ipswich Town earlier in the summer, while Celtic were also credited with an interest.
However, speaking to BT Sport ahead of the club’s 0-0 draw with Ross County in the Betfred Cup on Friday night, Lennon categorically stated that the McGinn is not available.
“I can’t guarantee it but he’s not for sale,” he said. “It’s going to take a huge bid from any club to take John away from us, £4-5 million. He’s still got a bit to do but already he is a quality player. He’s a Scottish international.”
The Hibs boss used the example of the fees paid in England for players who have little top-level experience in the hope it will either scare suitors off or result in a substantial windfall for the Easter Road side.
“There’s a market out there,” Lennon explained, “we all know the market. We sit on the border of England where people like Britt Assombalonga are going for £15 million from Nottingham Forest to Middlesbrough without playing in the top league.
“I have got a proven international who is 22. He’s not even anywhere near his peak yet but we already know what a good all-round player he is. He’s one of the best players in Scotland for his age.”
Lennon noted that McGinn is still a raw talent and has facets of his play which need improvement, but the potential is for one of the best the country has to offer.
“He’s got a bit to do,” he said. “There’s time where he can be inconsistent with the ball, he’s got a great array of passing, he’s very strong for his age, he’s got a stellar left-foot, he’s got goals from midfield.
“He’s got a very, very good engine, box-to-box. When he’s in the mood he is a match for anyone in the country.”