A disciple of Mike Leach, who was Stoops' first offensive coordinator at Oklahoma in 1999, Riley, 31, is considered to be one of the up-and-coming offensive minds in college football, calling plays for an East Carolina attack that ranked fifth in the country in total offense this season.
"Lincoln brings a fresh perspective to our program that I believe will help us maximize our potential offensively," Stoops said in a release. "He owns a consistent track record of implementing innovative offensive concepts during his career and has a history of developing productive offensive players. He has been mentored by a number of successful offensive coaches during his career, while developing his own unique offensive approach.
"Lincoln is also a talented recruiter who I'm confident will help attract top-flight talent to the University of Oklahoma. Our student-athletes and our staff will benefit from his skills and passion for the game. We are excited that Lincoln and his family are joining the Sooners."
Riley has been East Carolina's offensive coordinator, quarterbacks coach and associate head coach since 2010. The Pirates led the American Athletic Conference this season in total yards per game (533), yards per play (6.48) and third-down conversion rate (47.4 percent).
Before that, he was an assistant under Leach at Texas Tech, where he coached receivers from 2007 to 2009. After Leach was suspended for the 2009 Alamo Bowl, interim coach Ruffin McNeill tabbed Riley to call plays in the Red Raiders' 41-31 victory over Michigan State.
Weeks later, McNeill was hired to be the head coach at East Carolina, and he brought Riley with him to be his offensive coordinator.
Riley takes over for Josh Heupel, who was fired after a disappointing 8-5 season for the Sooners. Heupel, who led the Sooners to the 2000 national championship, had been Oklahoma's playcaller the past four seasons.
The Sooners are also searching for a wide receivers coach after parting ways with longtime assistant Jay Norvell.
ESPN's Brett McMurphy contributed to this report.