Ryan Tubridy will succeed Pat Kenny as the presenter of the Late Late Shownext season.
Tubridy who has presented Saturday's Tubridy Tonightsince 2004, will become the station's most experienced chat show host when Kenny steps down after 10 years in the Late Late Showat the end of the month.
Speaking about his appointment Tubridy said he is “deeply humbled” to be asked to host the “extraordinary programme”.
He said: “The job doesn’t come along very often..it was too hard to say no to such an offer.”
He added that he plans to give the show a “real 21st century twist”.
Turbridy will enter the hot seat of the world world’s longest running chat show on 5 September 2009 and the series will run to the end of May 2010.
RTÉ's Managing Director of Television Noel Curran said it was an opportunity to "look afresh" at the Late Late Show.
Tubridy Tonightwill be scrapped in the Autumn.
"We want to look again at our Saturday night schedule," Mr Curran said.
Kenny will begin a new current affairs show in the Monday night slot vacated by Questions and Answers.
According to RTÉ, it will be a mix of analysis, debate and satire.