Newcastle Rugby Ltd, the company that owns the city's union and league clubs, has purchased the freehold for Kingston Park from Northumbria University.
The deal brings the venue back within the rugby club's control for the first time since it was sold to the Northern Rock bank in 2007.
Newcastle Rugby chairman Semore Kurdi said the move was "very significant".
Northumbria, who owned the ground since 2008, will continue to play league and union matches at the ground.
Kurdi said the ground purchase "secures the long-term future of both Newcastle Falcons and Newcastle Thunder at Kingston Park Stadium".
He added: "It will also give us a permanent home from which we can continue the outstanding work of the Falcons Community Foundation as we look to grow both codes of rugby across the North East and Cumbria."