The Roar hitmaker said she is thrilled at the prospect.
Katy, 32, says: “I am honoured and thrilled to be the first judge bringing back the American Idol tradition of making dreams come true for incredible talents with authentic personalities and real stories.
“I’m always listening to new music, and love discovering diamonds in the rough – from mentoring young artists on my label, or highlighting new artists on my tours, I want to bring it back to the music.”
The network made the big announcement at its Upfront presentation in New York City on Tuesday.
The pop star teased a major announcement was coming when she confirmed a Times Square billboard featuring an eye illustration was one of her ads.
When a fan on Twitter asked if it was about her album or a single, Katy responded, “guess again”.
She all but confirmed the Idol rumours when she appeared on The Ellen DeGeneres Show on Tuesday.
ANNOUNCEMENT: Katty on The Ellen DeGeneres Show
“Idol is coming back,” Ellen DeGeneres, a former Idol judge, said, which Katy responded to with a simple nod. “Supposedly, you’re going to be the first announcement – that you’re going to be a judge on the new American Idol.”
Katy responded: “Judge not lest ye be judged. But, they didn’t say anything about constructive criticism and I’m good at that.”
The singer served as a guest judge on the original series in 2009 after Paula Abdul left the judges’ table.
Idol ended its 15-season run in 2016 and will be revived by ABC earlier this month. At its peak, the show had more than 30 million viewers.
Ben Sherwood, co-chairman, Disney Media Networks and president, Disney ABC, said in a statement: “American Idol on ABC... that has a nice ring to it.
“Idol is an entertainment icon... America, get ready for the return of a bigger, bolder and better-than-ever Idol.”
American Idol will debut on ABC in 2018.