Oldest champions: before 2000
Oldest fighters to win an undisputed UFC title, by age on the day.
Reigns are derived from championship bouts. When a belt was vacated or stripped outside a title fight, the reign is shown ending at the next title fight in that division, so a few run long; a title awarded without a fight (José Aldo's in 2010, for one) starts at the champion's first UFC title fight.
7 fighters.
| # | Fighter | Age | Division | Won | Ended |
|---|---|---|---|---|---|
| 1 | Maurice Smith | 35 years, 226 days | Heavyweight | Jul 27, 1997 | Dec 21, 1997 |
| 2 | Randy Couture | 34 years, 182 days | Heavyweight | Dec 21, 1997 | May 7, 1999 |
| 3 | Bas Rutten | 34 years, 72 days | Heavyweight | May 7, 1999 | Nov 19, 1999 |
| 4 | Mark Coleman | 32 years, 49 days | Heavyweight | Feb 7, 1997 | Jul 27, 1997 |
| 5 | Pat Miletich | 30 years, 221 days | Welterweight | Oct 16, 1998 | May 4, 2001 |
| 6 | Kevin Randleman | 28 years, 101 days | Heavyweight | Nov 19, 1999 | Nov 17, 2000 |
| 7 | Frank Shamrock | 25 years, 13 days | Light Heavyweight | Dec 21, 1997 | Apr 14, 2000 |