A formal announcement is expected soon.
The contract is for eight years and a total of roughly $24 million.
Holtmann spent the past three years at Butler and led the Bulldogs to three straight NCAA Tournament appearances. He won four NCAA Tournament games in those three seasons and advanced to the Sweet 16 this past March.
So Ohio State's search to replace Thad Matta -- who was removed Monday in a surprising development -- lasted just five days. But it was a wild five days that saw a list of possible candidates start with Arizona's Sean Miller, Indiana's Archie Miller, Xavier's Chris Mack and Billy Donovan of the Oklahoma City Thunder. The list then, on Wednesday, included Fred Hoiberg of the Chicago Bulls and Creighton's Greg McDermott -- both of whom publicly removed themselves from consideration within 24 hours of each other.
All the while, Holtmann was there.
The 45-year-old was identified as a candidate early. But OSU's search didn't completely turn his direction until Thursday afternoon. After that, though, a source told CBS Sports, things progressed quickly. And now Butler athletic director Barry Collier finds himself in the unfortunate position of having to conduct a coaching search only a few weeks before the July evaluation period begins.