The 'Super Bass' hitmaker and the country singer - who quit the Australian version of 'The Voice' earlier this month - will join fellow newcomer Mariah Carey and long-serving panellist Randy Jackson on the US talent show, and Keith is ''so excited'' to have landed the role.
He wrote on twitter: ''SO excited to be joining the team on @AmericanIdol!!!!!! - KU#idoljudges (sic)''
'American Idol' host Ryan Seacrest also took to the social networking site to confirm the four judges will be on the panel for the forthcoming 12th season of the show.
He tweeted: ''It's official! Your Season 12 Idol judges are Mariah Carey, Randy Jackson, Nicki Minaj and Keith Urban. Meet the judges (sic)''
Mike Darnell, President of Alternative Entertainment for Fox, believes the talent show has recruited one of the ''most exciting judging panels around'' for the forthcoming season - which is due to air in January - after Nicki and Keith replaced outgoing judges Jennifer Lopez and Steven Tyler.
He said in a statement: ''Nicki's an unbelievably captivating international phenomenon who has made an indelible mark on rap and pop.
''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-favourite Randy, chart-toppers like Nicki and Keith and our incomparable host Ryan, we've put together one of the most exciting judging panels around.''
Randy - who has been a judge on the programme since it began in 2002 - signed a new deal to remain on the show after talks with Spanish singer Enrique Iglesias broke down.
He tweeted: ''Just heard Randy is back on Idol. Right decision.''
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