Following months of speculation over who would replace Jennifer Lopez and Steve Tyler, Fox TV confirmed the new additions yesterday.
"Nicki's an unbelievably captivating international phenomenon who has made an indelible mark on rap and pop," said Fox's president of alternative entertainment Mike Darnell.
"And Keith is another great addition to Idol he's one of the biggest stars in country music and I know that our fans and contestants will fall in love with him."
"With an unparalleled star like Mariah, fan-favorite Randy, chart-toppers like Nicki and Keith and our incomparable host Ryan [Seacrest], we've put together one of the most exciting judging panels around."
Fresh from announcing his departure from The Voice Australia week, Keith ecstatically took to Twitter this morning to confirm the news.
"SO excited to be joining the team on @AmericanIdol!!!!!!" he wrote.
American Idol host Ryan Seacrest tweeted the first picture of the four judges together overnight (see above pic).
"It's official, your new #IdolJudges are @MariahCarey, @NickiMinaj, @KeithUrban and @Yo_RandyJackson!" he tweeted.
All of the judges arrived separately for the first day of auditions in New York City at the weekend. Keith looked relaxed in casual gear, while Mariah went for a demure black number with shades, and Nicki brightened up the palette with her trademark fluoro hair and dangerously tight, camel-toe-revealing pants.
Related: From TV to superstar: First audition tapes of stars who've made it big