At least 200 jobs are to be created over the next three years following an investment by RSM UK into sister accountancy firm, RSM Ireland.
The injection, understood to be in the region of €20m, will result in RSM UK acquiring its Irish counterpart from the current board.
RSM Ireland said the move would allow it to accelerate long-term growth and drive increased competition in the professional services sector in Ireland.
It will also result in RSM Ireland being able to offer a wider range of services, including in areas such as cyber security, ESG, public sector, technology, life sciences and financial services.
RSM Ireland currently employs 200 people here.
Both firms will continue to operate separately, with founding partners of RSM Ireland, John Glennon, Catherine Corcoran Gearty and Aidan Byrne remaining in the firm in strategic leadership roles.
Niall May will succeed John Glennon as managing partner in January 2024.
"This is an incredibly exciting day for RSM Ireland," Mr Glennon said.
"This investment will enable us to accelerate our investment in Irish capabilities, deepen our service offerings and expertise, and expand the breadth of services we offer to our clients."
"It will also offer greater opportunities to our people to progress their careers and achieve their potential."
RSM Ireland was founded in 1987 and is now among the top ten and fastest growing accountancy businesses in this country.
RSM UK employs 4,700 staff and reported a 14.3% increase in annual revenue to record €559.3m in its last financial year.
"This important investment marks a major statement of intent to accelerate growth and capture greater market share in Ireland," said Rob Donaldson, CEO for RSM UK.
"It also builds on our drive to become an ever more formidable competitor, both here in the UK and in Ireland."
