A company owned by businessman Denis O'Brien has purchased Today FM, FM104 and Donegal's Highland Radio from Emap.
An Emap statement to the London Stock Exchange said that Mr O'Brien's Communicorp paid €200m (£135m) for the three stations.
London based Emap, the publisher of Closer and Grazia magazine, decided to sell its radio stations in Ireland some months ago so it could concentrate on digital media.
Among the bidders for the stations were The Irish Times, TV3, a group involving businessman Ulick McEvaddy, UTV and Scottish company New Wave Media.
There are competition issues for Mr O'Brien as his company already owns Newstalk and 98FM, and the takeover has to receive approval from the Competition Authority and the Broadcasting Commission of Ireland. The final say rests with the Minister for Enterprise, Trade & Employment.
'The sale is conditional upon obtaining certain necessary regulatory clearances which are expected to be obtained in the second half of our financial year', Emap's statement said today.
Emap's regional manager Willie O'Reilly says that every media acquisition or change of ownership must be referred to the Competition Authority and this deal is no different.
He says this issue should be cleared up in four or five months, and that the Broadcasting Commission of Ireland rules currently say any existing entity can own up to eight radio stations, which is what Communicorp will own.
In a statement Communicorp said the agreement offers the security of a committed investor determined to develop commercial radio over the long term and brings the stations back into Irish ownership.
Emap acquired the three stations with Scottish Radio Holdings (SRH) in 2005.
In the year to 31 March, the business had revenue of £21m and operating profit of £7m.
The sale is expected to be tax free for Emap with the proceeds used to pay off the group's debt.