The Croatian midfielder is believed to be high on Sir Alex Ferguson's shopping list after playing a key role in the London club clinching a place in next season's Champions League.
But Redknapp is in no mood to lose one of his prized assets as he looks to challenge the big boys next season.
Despite talk of a £25million United raid, Redknapp told The Sun: "There's no chance of it happening at all. Luka's key to everything that's happening at this place.
"Everybody knows what I think of him. And if you want to move on to higher levels you don't start flogging off your best players - to anyone."
Redknapp says he won't be moving for Manchester City's Stephen Ireland or Bolton defender Gary Cahill.
And it appears his biggest summer aim is hanging onto Modric.
He added: "I have an excellent squad and - I stress - Luka Modric is going to remain a part of it."