Bryan and Richie will join previously-announced judge Katy Perry, whose participation became public knowledge shortly after ABC announced in May the reality singing competition would be returning to television on a new network. (All 15 prior seasons of American Idol aired on Fox).
The three judges will appear on Good Morning America together on Wednesday, October 4, and Ryan Seacrest will reprise his role as host.
"I'm excited at the chance to help some deserving artists reach their dreams," Bryan said in a statement. "To be in a position in my career to help facilitate this along with the other judges is just a complete honor. It's going to be a blast!"
In a video Bryan posted Friday on Twitter, he added that he's "proud" to take on the position and can't wait to see "all the talent out there that America has" to offer.
Bryan is a two-time Academy of Country Music and Country Music Association Entertainer of the Year, a five-time host of the ACM Awards, and the 2017 Super Bowl LI National Anthem performer.
Bryan has placed 18 singles at No.1 and sold over 10 million albums. He has also performed for millions of fans on tour and recently debuted a new single, "Light It Up," off his new album due out later this year.
"I am very excited to be joining Katy, Luke and Ryan on American Idol," Richie said in a statement. "As a singer, songwriter and producer, I feel I can bring a great deal of experience to the table. It's going to be so much fun!"
Richie is one of only two songwriters in history to achieve the honor of having No. 1 records for nine consecutive years.
Richie has sold more than 100 million albums worldwide and won Oscar, Golden Globe, and Grammy Awards. Richie is probably best known for his hits such as "Endless Love," "Lady," "All Night Long," and "Stuck on You."
"Luke and Lionel are the perfect additions to round out our panel of judges for American Idol on ABC," said ABC Entertainment president Channing Dungey.
"In their respective genres of music, both Luke and Lionel possess insurmountable popularity and award-winning talent that are undeniable, and we are lucky that they will help in paving the way for hopefuls pursuing their dreams on our stage."
Trish Kinane, an executive for the show's production company FremantleMedia North America, explained that a hasty decision was certainly not made for Idol's new lineup of judges.
"We have taken our time to get the right mix of amazing talent for the new Idol judging panel," Kinane said.
"Our viewers expect musical credibility, passion and a true concern for the contestants; and with Luke Bryan and Lionel Richie joining the brilliant Katy Perry, we have two more world-class musical powerhouses eager to get to work and identify the next generation of superstars."
Perry was signed to a $25 million deal to judge American Idol, while TMZ reported Bryan will receive about $13 million and Richie will earn about $10 million for doing the show.
Other celebrities who were reportedly in talks with ABC over the last several months to potentially judge ABC's revival include Charlie Puth, Keith Urban, and former Idol finalist Chris Daughtry.
American Idol, which debuted on Fox in 2002, is expected to premiere on ABC sometime in early March.