"American Idol" and ABC made it official Tuesday ... they've bagged Katy Perry to be the lead judge when the show returns next year.

ABC Entertainment President Channing Dungey made the announcement Tuesday -- as we first told you she would -- at the network's Upfronts in NYC. Katy wasn't there for the big reveal, but said in a statement she was "honored and thrilled to be the first judge bringing back the American Idol tradition of making dreams come true."

The network didn't have anything else to say about its 'Idol' reboot. Our sources say it's still a near certainty Ryan Seacrest will host. Zippo on the other 2 judges too.

We broke the story ... 'Idol' honchos don't feel it's essential to the show's success to get another big name singer now that they have Katy. We're told they'll target songwriters and industry execs.

Stay tuned.