Legendary coach Bob Stoops, 56, will retire after 18 seasons leading the Oklahoma Sooners and is preparing to inform his team on Wednesday.

Stoops leaves Oklahoma with a 190-48 record (101-9 at home), 10 conference titles in the Big 12 and a national crown after winning 2001 BCS Championship Game. He is the Sooners' all-time winningest coach and will remain with the university as special assistant to the athletic director.

Stoops, a six-time Big 12 Coach of the Year and two-time national coach of the year, will remain as special assistant to the athletics director.

"After 18 years at the University of Oklahoma, I've decided to step down as the head football coach. I understand there has been some speculation about my health. My health was not the deciding factor in this decision and I've had no incidents that would prevent me from coaching," Stoops said in a school release.

Offensive coordinator Lincoln Riley, 33, has been named Stoops' permanent replacement. Riley was given a three-year contract extension in May that paid him $1.3 million annually.

"I feel the timing is perfect to hand over the reins. The program is in tremendous shape. We have outstanding players and coaches and are poised to make another run at a Big 12 and national championship. We have new state-of-the-art facilities and a great start on next year's recruiting class. The time is now because Lincoln Riley will provide a seamless transition as the new head coach, capitalizing on an excellent staff that is already in place and providing familiarity and confidence for our players," Stoops continued. "Now is simply the ideal time for me and our program to make this transition."

Added Riley: "I'm sincerely honored to be given this opportunity to be the head football coach at the University of Oklahoma. I want to thank Coach Stoops for bringing me here two years ago and making me part of the Sooner family. He is one of the greatest coaches in the history of the game, at any level. I'm absolutely thankful for our friendship and for the mentorship he has provided. Coaching at Oklahoma is a dream come true for me and my family."

While the timing of the announcement is surprising -- to say the least -- it's worth pointing out that Stoops, a noted family man, recently purchased a home for $2.25 million in the Gold Coast area of Chicago.

With Stoops out of college football, Iowa's Kirk Ferentz is now the longest tenured FBS coach at the same program.

A defensive back at Iowa (1979-82), Stoops served as a graduate assistant at his alma mater and got his first big break coaching the secondary for Kansas State in 1989. He was promoted to co-defensive coordinator with the Wildcats in 1991 and was picked up by Steve Spurrier to serve as assistant head coach and co-defensive coordinator for Florida in 1996 after the Gators' defense gave up 62 points in the 1996 Fiesta Bowl.

Stoops made a name for himself in Gainesville, Florida, turning around a defense that held undefeated Florida State to 20 points in the 1997 Nokia Sugar Bowl. Florida claimed its first national championship in that game and went 20-4 over the next two seasons before Stoops left to take over Oklahoma at age 39.

He turned a program that had gone five straight seasons without a winning record into a team that finished second in the Big 12 South his first season, posting a 7-5 record in 1999. The very next year, the Sooners went undefeated and beat the Seminoles for the 2000 national championship.

Stoops won 10 or more games in 14 of his 18 seasons and ran roughshod over the Big 12 during his tenure at Oklahoma with 10 conference titles, including three straight from 2006-08 and consecutive crowns over the final two years of his career in 2015-16.

OU returned to the national championship three times after 2000 but lost in all three of his appearances. The Sooners fell to LSU in 2003, USC in 2004 and Florida in 2008.

Oklahoma finished the season ranked in the AP Top 25 in all but three of Stoops' campaigns with 11 placements inside the top eight of the poll in 18 years. He also led the Sooners to 11 BCS, College Football Playoff or New Year's Six bowl games and is the only coach to win the Fiesta Bowl, Orange Bowl, Rose Bowl and Sugar Bowl along with a national championship.