"For personal reasons, I'm unable to continue on American Idol. This has been one of the hardest decisions I've ever had to make, but I know it's necessary," Kenedi wrote in an Instagram post.
"I'm so grateful to American Idol, the judges, the producers, the amazing contestants, and all the fans who have supported me."
"Thank you for giving me such an amazing opportunity to share my voice, chase my dreams, feel so much joy and happiness doing what I love, and make lifelong friends along the way," she concluded.
American Idol's production company Fremantle Media also told People that producers are sad to see such a talent like Kenedi go.
"We are disappointed to see Kenedi leave, but we are excited to watch this celebratory 20th season unfold with the incredible talent vying to be the next American Idol," the company said in a statement.
American Idol host Ryan Seacrest first announced Kenedi would be leaving the competition during Monday night's broadcast, which featured the second half of this season's Top 24 performances that were previously filmed at Disney's Aulani Resort in Hawaii.
Because all of the solos were pre-taped, Idol decided to air Kenedi's gripping rendition of "Human" by Christina Perri, which included impressive runs and a masterful use of falsetto.
"You might have noticed that there was no voting information during Kenedi's performance just now," Ryan explained in a special announcement following her stunning performance.
"Since we taped these shows in Hawaii earlier, Kenedi has decided to withdraw from our show for personal reasons. We send her well wishes."
Ryan added, "We have incredible talent on this historic season, with more iconic Idol performances coming up for you right now."
Kenedi first shocked the judges with her powerful and soulful voice during the initial round of auditions, when she played the piano and sang "Applause" by Lady Gaga.
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Katy, Lionel and Luke gave the blonde beauty a standing ovation and gushed about her potential in the music industry.
"I mean, my head is spinning... We've definitely got us a superstar on our hands!" Luke, 45, said after Kenedi's audition.
And Katy, 37, exclaimed how she felt "threatened" by the young vocalist, adding, "I'd like to be your manager and your producer! I don't know how you haven't been recruited. You check every box... Get ready to become your own hero."
And Lionel, 72, said the teenager had "answered" the judges' "prayers," saying she could very well be the next "thing" in the music business.
Katy appeared to suggest Kenedi could become the next Kelly Clarkson -- who won American Idol's first season and went on to have an incredibly successful career -- during a recent interview with People.
"I was listening to everyone's sound check, and everybody sounded good," Katy shared in Hawaii.
"But there were a few where I was like, 'Oh my God.' There's one in particular I have my eye on. I think that she is probably the biggest star that American Idol has ever found!"
American Idol currently airs on Sunday and Monday nights at 8PM ET/PT on ABC.
American Idol will reveal its Top 20 contestants for Season 20 on Sunday, April 17.
The show's Top 14 singers will then be unveiled on Monday, April 18, with home viewers picking 10 of the contestants and the judges choosing four more hopefuls to advance in the competition.