Kostya Tszyu vs. Leonardo Mas
1997-01-18 : Kostya Tszyu 139½ lbs fought without result Leonardo Mas 139½ lbs by NC in round 1 of 12
- Location: Thomas & Mack Center, Las Vegas, Nevada, USA
- Referee: Joe Cortez
- Judge: Ray Wheatley
- Judge: Chuck Giampa
- Judge: Bill Graham
- International Boxing Federation Light Welterweight Title (5th defending of Tszyu)
- Weights: 139.5 lbs (each)
- Promoter: Top Rank
- Mas was dropped three times, but the final knockdown occurred on a break and he could not continue.
- Originally ruled a technical draw, but later changed by the Nevada State Athletic Commission to a no contest.