1999–2000 LEN Champions League
The 1999–00 LEN Champions League is the 37th edition of LEN's premier competition for men's water polo clubs. It ran from 27 October 1999 to 27 May 2000, and it is contested by 28 teams. The Final Four took place on May 26 and May 27 in Bečej.
Preliminary round
| Key to colors in group tables |
| Group winners and runners-up advanced to [|Final four] |
Blue Group
Red Group
Final Four ([Bečej])
Final standings
| Team | |
 Bečej | |
 HAVK Mladost | |
 BVSC | |
| POŠK |