The future of the historic store had remained unclear, along with a number of other sites, after the billionaire businessman bought the House of Fraser chain out of administration.
Sports Direct has bought the Frasers building from Glasgow City Council.
The purchase secures hundreds of jobs at the vast 350,000 square feet store. It opened as the first House of Fraser department store in 1849 under the name Arthur and Fraser.
Sports Direct said today: “Sports Direct intends to continue to operate the property as Frasers and will invest in the property to further elevate and enhance this iconic department store.
“The consideration payable for the property is £95m, which will be funded from the group’s cash resources. Completion is to take place in January 2020.”
The bumper deal means that Ashley has paid more for the freehold to the Glasgow building than the £90m he paid for the entire House of Fraser chain when he moved to save it from administration in August, on top of an existing 11 per cent stake he owned.