William Henry Grigsby (born March 19, 1970 in Saint Paul, Minnesota, USA) is an American professional boxer.
Grigsby turned pro in 1988 and lost his second professional fight, to flyweight legend Michael Carbajal who was making his professional debut. In 1998 he captured the vacant IBF light flyweight title by decisioning Ratanapol Sor Vorapin. He defended the belt once before losing it to Ricardo Lopez in 1999. In 2000 he captured the WBO light flyweight title with a decision win over Nelson Dieppa, but was stripped of the belt after the fight for testing positive for marijuana. The fight changed to no decision. He fought sporadically before capturing the IBF light flyweight title with a decision over Victor Burgos in 2005. He lost the belt in his first defense to Ulises Solís, and lost a rematch with Solís in 2007.
| Preceded by Mauricio Pastrana Stripped |
IBF Light Flyweight Champion 18 Feb 1998–2 Oct 1999 |
Succeeded by Ricardo Lopez |
| Preceded by Victor Burgos |
IBF Light Flyweight Champion 14 May 2005–7 Jan 2006 |
Succeeded by Ulises Solís |