| WEC 20: Cinco de Mayhem | |
| Promotion: | World Extreme Cagefighting |
| Date: | May 5, 2006 |
| City: | Lemoore, California |
| Previousevent: | WEC 19: Undisputed |
| Followingevent: | WEC 21: Tapout |
WEC 20: Cinco de Mayhem was a mixed martial arts event held by World Extreme Cagefighting that took place on May 5, 2006 at Tachi Palace Hotel & Casino in Lemoore, California. WEC 20s main event was a heavyweight bout between Brian Olsen and Mike Kyle.