The deal forms a "key part" of the Srivaddhanaprabha family's plans to safeguard the Championship team's long-term future.
The stadium purchase, from an American pension fund manager, by the club's owners has been made through their K Power Holdings Co Ltd.
Leicester City vice chairman Aiyawatt Srivaddhanaprabha said: "It has always been part of our long-term vision to put the stadium back where it belongs, into the hands of the football club.
"Our plan is to bring long-term sustainable success to Leicester City Football Club. Purchasing the stadium was always a key element in this plan.
"The previous stadium owners have always been very cooperative. Whilst there are no immediate plans to alter the structure or design of the stadium site, the increased flexibility through direct ownership ensures that the football club can freely adjust to the changing needs of its supporter-base for the future."
In September 2012, the Srivaddhanaprabha family placed Leicester City under the direct ownership of King Power International (KPI), the parent and holding company of the King Power group of companies.
Leicester City chief executive Susan Whelan added: "The stadium already bears the proud name of King Power, but this latest development truly makes the home of Leicester City part of the Srivaddhanaprabha family's central business and sporting interests.
"For firstly the football club, and now its magnificent stadium, to be aligned so closely with a group of companies of such global success and repute can only be beneficial for the future of Leicester City, while the removal of all significant third-party debt ensures a more sound financial position from which the club can progress."