RTÉ has confirmed that Kevin Bakhurst, the managing director of news and current affairs, is to leave the organisation in October.
He will take up a position as content group director for Ofcom, the communications regulator in the UK.
Mr Bakhurst, who joined RTÉ four years ago, also served as deputy director-general at the broadcaster.
He was most recently acting director-general, following the departure of Noel Curran.
In a statement, Mr Bakhurst said: "I have had a wonderful four years at RTÉ with the most talented, professional and dedicated team of journalists - and great and creative colleagues across the organisation."
He added: "I am in particular immensely proud of the recent coverage of the General Election and the RTÉ 1916 commemorations; of the range of investigations we have carried out; but also of the fair, thoughtful and engaging reporting of stories day-in, day-out.
"It has been an absolute privilege to work for the national broadcaster during a time of change and renewal and I wish Dee Forbes and the whole organisation the very best for the years to come.
"I also wish the very best to the rest of Ireland's vibrant media who play a crucial role during challenging times."
RTÉ Director-General Dee Forbes said that Mr Bakhurst "led RTÉ News & Current Affairs decisively through a period of intense change and development".
She said that "his contribution, inside the newsroom, and beyond, has been significant".
"I'd like to warmly congratulate Kevin on this new role and wish him the very best for the future," she added.
As managing director, Mr Bakhurst led the creation and development of the RTÉ Investigations Unit and its subsequent investigative programming, including landmark investigations of creches, care facilities, the charity sector and criminality.
During his tenure, RTÉ's television bulletins were revamped and the organisation's digital news and social media presence rapidly expanded.
RTÉ also managed to secure the future of the regional studios by building partnerships with local Institutes of Technology during his time at the broadcaster.
Mr Bakhurst was previously deputy head of the BBC Newsroom, overseeing BBC TV news, radio news and the BBC News website.
Speaking on RTE's News at One, Mr Bakhurst said leaving the organisation is a "big wrench", but his decision to leave is based on a "fantastic job".
"I wasn't looking for it. I was approached about it. I wasn't even looking for a job in the UK - I'm very, very happy here. But a job came up. It's very unusual for these big jobs and new challenges to come up. It's a fantastic job."
He said his decision was not influenced by the fact that he was not appointed director general, saying "it wasn't a factor".
"I've done four years here. It's been a fantastic four years - probably some of the best years of my career. I've thoroughly enjoyed it. I work with great people here and I think we've done a lot in terms of the journalism here; getting the investigations unit up and running; some of the investigations we've done; just the daily coverage.
"I'm hugely attached to the people I work with here, so it's a big wrench going, but these opportunities are few and far between when they come up and I leave RTÉ, hopefully, in a very strong position."
He said the issue of public funding is the biggest challenge facing RTÉ.
"If Ireland is to continue having a powerful and important national broadcaster, that is certainly something that people should be turning their attention to."