Luke Martinez added 17 points for the Cowboys (13-2), Washington 14 and Adam Waddell 10.
Both teams were hot from 3-point range. Wyoming made 11 of 24 (46 percent) and Utah Valley 7 of 16 (44 percent).
Williams' 3-pointer pulled the Wolverines within 69-68 with 2:26 left. Then he put Utah Valley ahead 70-69 with a jumper 31 seconds later.
But Washington converted a layup on the next possession for a 71-70 lead, and Wyoming finished it with five free throws.
Wyoming had been the only team in the nation not to allow an opponent more than 60 points.
- Sports & Recreation
- Sports & Recreation/Basketball
- Isiah Williams