Word of the announcement broke on The MMA Hour.
Sean Sherk just announced his retirement.— Ariel Helwani (@arielhelwani) September 2, 2013
"The Muscle Shark" finishes his career with an official record of 36-4-1, having gone 8-4 in 12 total UFC bouts.
His career peak occurred in 2006 when the dominant wrestler dropped to 155 pounds and fought Kenny Florian for Jens Pulver's vacant UFC Lightweight Championship, the first time the title was brought back to the promotion since 2004.
Sherk survived some vicious cuts due to elbows from Florian and was able to wrestle and ground and pound his way to a brutal five round unanimous decision victory to capture the belt. He would defend his championship against Hermes Franca, but was stripped of the title and suspended after failing a post-fight drug screening, putting an end to his 420 day title reign.
Upon returning from suspension, he was defeated by B.J. Penn with the title on the line, losing via TKO at the end of the third round of UFC 84 in 2008. He would never get another opportunity to vie for the belt, closing his career with a 2-1 mark while raking in two "Fight of the Night" bonuses.
Sherk was last seen competing three full years ago, winning a close split decision over Evan Dunham. He was plagued by injuries towards the tail end of his career and was never able to get back into the Octagon.
According to a press release from his sponsor Training Mask, the 40-year old Minnesota native plans to maintain his involvement at Training Mask while coaching MMA, and teaching seminars. Sherk is also continuing a successful career in real estate investment.