The judge, who has appeared on all bar one of the show’s 14 series, will not feature in the 2018 episodes.
A statement from Louis, released on Thursday evening, reads: “I’ve had a fantastic 13 years on ‘The X Factor’ but the show needs a change and I’m ready to leave.
“I’m looking forward to another series of ’Ireland’s Got Talent, going back to my day job as a manager, writing my memoirs and seeing the world!”
The press release announcing Louis’s decision declared that the development marks “the beginning of a new era for the UK’s most popular music talent show”.
Bosses have also confirmed that Sharon Osbourne will only serve as a judge on the live shows, not the audition stages.
“I can’t wait to get back to the judges’ desk,” she said in a statement. “I love the new format.”
Simon Cowell will return in his usual role, joined by three new judges.
While it’s long been rumoured that Nicole Scherzinger will also be leaving, the mention of “three new judges” confirms the US superstar won’t be back.
However, the release makes no mention of her by name. HuffPost UK has contacted Nicole’s representative for comment.
Open auditions for the 2018 series have already taken place across the country. The first filmed ones will take place at Wembley Arena in the coming weeks.