NEW YORK >> Fox is lowering the curtain on “American Idol,” ending a series that dominated television throughout the 2000s and made stars of the likes of Simon Cowell, Kelly Clarkson and Carrie Underwood.

The network announced Monday that “American Idol” will go off the air after its 15th and final season next spring. The cast from the past few seasons, with Ryan Seacrest as host and Jennifer Lopez, Keith Urban and Harry Connick Jr. as judges, will return for a season-long celebration of the show’s history.

“It was not an easy decision.’ American Idol’ has been such a vital part of Fox for its run,” said Gary Newman, Fox Television Group chairman and CEO. He promised a season-long celebration that matches the show’s significance, with the suggestion that its big-name contestants and past judges may be involved.

“American Idol” faded over the past few years, eclipsed in the music competition genre it pioneered by “The Voice” on NBC. Personnel changes didn’t help, and neither did tinkering with the format, as the show fell victim to what usually kills off most television series — old age. Still, it was a solid performer for a Fox network that struggles in the ratings.

Dana Walden, co-chairman and CEO of the Fox Television Group, described it as a “pretty emotional decision” to end “American Idol.”

Fox and the show’s producers were discussing how the series would continue, but ultimately “we all arrived at the conclusion that it was time to bring the show to an end,” said Newman. “But we wanted to do it in a way that was special and celebratory.”

“Idol” was a quick hit, with fans following contestants who sought the prized “yellow ticket” to Hollywood and a chance at stardom. In the early years, “American Idol” also showed many of the cringe-worthy auditions of contestants with no hope of winning, but has generally resisted those recently.

Simon Cowell, the Brit with a tart tongue and honest assessments, became a star as judge, along with his fellow originals, Paula Abdul and Randy Jackson.

“‘American Idol’ has been a big part of my life for so long, it’s frankly hard to imagine it without it,” said Seacrest, who was co-host of the show with Brian Dunkleman on the first season, and solo host for all the others. “It’s been a remarkable journey, and I feel very fortunate to have been part of a show that made television history in countless ways. It’s a show about chasing and fulfilling dreams and, truth be told, it helped some of my own dreams come true, too.”

The big-voiced Clarkson became a major pop star after winning “Idol,” and Underwood is a solid performer on the country charts. Personalities like Adam Lambert and Clay Aiken also became household names after competing on “Idol.”

Walden said there are no specific plans yet, but that several former contestants and judges have already expressed “a lot of enthusiasm” for coming back and celebrating the show’s legacy in its final year.

“We’re going to deliver a really special season next year,” Newman said.

The series averaged 12.69 million viewers during its initial run in 2002, but exploded quickly thereafter, reaching a peak average of more than 30 million viewers each episode in 2006, according to the Nielsen company. It continued averaging more than 20 million viewers an episode through the 2011 season, and that’s when the deteriorating in its popularity accelerated.

Its star at Fox was eclipsed this season by the music-based soap opera “Empire,” which will launch its second season in the fall. So far this year, “American Idol” is averaging 9.15 million viewers per episode, Nielsen said.

The show will run in a similar format next season as it has this year, airing Wednesday and Thursday nights starting in January for the beginning stages, then once a week on Thursday for the second part of the season, Fox said.

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Television Writer Lynn Elber in New York contributed to this report.