The first MMA heavyweight title was given to Mark Coleman after his submission victory over Dan Severn at UFC 12.
Mark Coleman [6-0] record before losing to:
Maurice Smith [4-7] at UFC 14.
Maurice Smith [6-7] record before losing to:
Randy Couture[3-0] at UFC 15.5.
Randy Couture [4-0] record before losing to:
Enson Inoue [8-3] at Vale Tudo Japan.
Enson Inoue [10-3] record before losing to:
Mark Kerr [11-0] at PRIDE Grand Prix 2000.
Mark Kerr [12-0] record before losing to:
Kazuyki Fujita [3-0] at PRIDE Grand Prix 2000.
Kazuyki Fujita [4-0] record before losing to:
Mark Coleman [9-4] at PRIDE Grand Prix 2000.
Mark Coleman [12-4] record before losing to:
Rodrigo Nogueira [12-1] at PRIDE 16.
Rodrigo Nogueira [19-1] record before losing to:
Fedor Emelianenko [12-1] at Pride 25.
Fedor Emelianenko [31-1] record before losing to:
Fabrico Werdum [13-4] at Strikeforce: Fedor vs. Werdum.
Fabrico Werdum [14-4]record before losing to:
Alistair Overeem [43-11] at Strikeforce: Overeem vs. Werdum.
One potentail area of dispute in determining a linear champion is determining the original champion. If you consider Royce Gracie the original openweight champion because of tournament wins in UFC 1, the road still leads to 'Reem.
Royce Gracie UFC 1 Champ. [8-0] record before losing to:
Harold Howard [1-0] via forfeit at UFC 3.
Harold Howard [2-0] record before losing to:
Steve Jennum [0-0] at UFC 3.
Steve Jennum [2-0] record before losing to:
Tank Abbott [2-1] at UU 95 - Ultimate Ultimate 1995.
Tank Abbott [3-1] record before losing to:
Dan Severn [6-2] at UU 95 - Ultimate Ultimate 1995.
Dan Severn [14-2] record before losing to:
Mark Coleman [5-0] at UFC 12.
And then, again, the road leads back to Alistair Overeem.
Even if you do not count Royce Gracie's loss to Harold Howard legit and follow his next loss to Sakuraba, you stil get Overeem.
Royce Gracie UFC 1 Champ [11-1] record before losing to:
Sakuraba [8-1] at PRIDE Grand Prix 2000.
Sakuraba [9-1] record before losing to:
Igor Vovchanchyn [34-2] at PRIDE Grand Prix 2000.
Igor Vovchanchyn [35-2] record before losing to:
Mark Coleman [10-4] at PRIDE Grand Prix 2000.
Mark Coleman [12-4] record before losing to:
Rodrigo Nogueira [12-1] at PRIDE 16.