McCullagh has been with RTÉ for 27 years.
David McCullagh, Prime Time presenter and co-host of This Week on RTÉ Radio One, will join Caitríona Perry as a newsreader on the Six One News from September of this year.
McCullagh's appointment follows the death of journalist Keelin Shanley, who tragically passed away at the age of 51 earlier this year.
In a statement issued by RTÉ on Friday (3 July), McCullagh said he was looking forward to the new role, "and continuing the work of our much loved colleague, Keelin Shanley".
Director of RTÉ News and Current Affairs Jon Williams said: "David is one of Ireland's most formidable journalists.
"For seven years, at Prime Time, he’s sought answers from scientists to Taoisigh, moderating - with Miriam - our Election 2020 Leaders’ Debate, and helping the programme reach some of the biggest audiences in its history during the Covid-19 lockdown.
"There could be no one better equipped to join Caitríona on Six One as Ireland emerges from this emergency facing some difficult challenges, and heads towards the centenary of the foundation of the State."
McCullagh joined the state broadcaster 27 years ago, and worked as a political correspondent before taking up his current role at Prime Time. He has also written four books on Irish history.
