One of the Republic's best known broadcasters Gerry Ryan has been found dead in his Dublin apartment.
The 53-year-old anchored a popular daily morning chat show on RTE's radio station 2FM.
"Mr Ryan was found dead in his apartment in Upper Lesson this morning," a senior Garda source said.
It is understood the death is not being treated as suspicious.
A Garda source said Ryan was found in his bedroom after officers were called to the scene when a friend couldn't gain access to the apartment in central Dublin.
The broadcaster announced a separation from his wife Morah in March 2008 after 26 years of marriage. The couple had five children together.
After a stint in pirate radio, the often controversial and outspoken DJ joined the Republic's state broadcaster RTE in 1979.
The Gerry Ryan Show began in 1988 and quickly became one of their most popular radio programmes.
Ryan has also hosted several television series including Secrets, Ryantown, Gerry Ryan Tonight, Gerry Ryan's Hitlist and Ryan Confidential.
In 1994 Ryan co-presented the 1994 Eurovision Song Contest with former newsreader Cynthia Ni Mhurchu.
RTE Radio One broadcaster Derek Mooney made a brief statement during his afternoon programme passing on condolences from colleagues to Ryan's family and friends.
Taoiseach Brian Cowen said he was deeply saddened to learn of Ryan's death.
"Gerry was a household name and a broadcaster of immense talent and popularity," he said.
"His legion of fans will all be greatly shocked to hear this sad news.
"He was one of the greats of modern Irish broadcasting on radio and television."
Mr Cowen said the popular Gerry Ryan Show on 2FM was compulsive listening for hundreds of thousands of people.
"As a broadcaster, Gerry Ryan was both informed and intelligent, forthright and articulate," he said.
"As a man, he was generous, famously irreverent and witty.
"I had the pleasure of meeting him many times, both in front of and away from the microphone.
"He was always engaging company and a man of considerable charm.
"He will be hugely missed by all those who had the good fortune to know him."
Mr Cowen also extended his sympathies to Ryan's family and friends.
Green Party leader and Environment Minister John Gormley said Ryan will be greatly missed, as a broadcaster, DJ and familiar voice to thousands of listeners every morning.
"His ability as a broadcaster to take both the serious and light-hearted stories was second to none," he said.
"His good humour concealed a keen intellect and a commitment to straight journalism - he was a fair and accurate commentator.
"His death is a tragic loss for the viewers and listeners of Ireland."
In a statement, RTE said Ryan's family were in "complete shock" and had appealed for privacy.
"It is with profound sadness that RTE has learned of the sudden death of broadcaster Gerry Ryan," the broadcaster said.
"The thoughts and prayers of all RTE staff are with Gerry Ryan's family and his friends."
In a departure from normal broadcasting, 2FM played uninterrupted back-to-back songs during the afternoon.
RTE Radio One cut short its afternoon schedule for a special tribute to the presenter.
Fellow RTE broadcaster and long-time friend Joe Duffy choked back tears live on air as he recalled the "bold schoolboy" he first met in 1979 at Trinity College Dublin.
"He was the best company you could ever have," he said.
"He was bold in every sense of the meaning of that word.
"He was brave in his broadcasting, he was brave in his life, he lived his life to the full.
"He was bold in the sense of being cheeky, bold in the sense of being arrogant, bold in the sense that you loved hanging around with the bold schoolboy in your class."
Duffy said his friend was the best company anyone could have, was insightful, very intelligent, extraordinarily generous and a great mimic.
Claire Duignan, managing director of RTE Radio, said Ryan complained of being unwell last night and told colleagues he did not think he would be able to do his show today.
"When he spoke with people to say he wouldn't be in today, they obviously expressed concern and asked did he need a doctor or anything like that," she said.
"But he said no, he was fine, but he wouldn't be in today."
Ryan was born in Dublin and worked for a time as an apprentice solicitor after studying law at University College Dublin.
After cutting his broadcasting teeth on pirate radio he moved to RTE, where he initially shared a late-night spot with the likes of Dave Fanning and Mark Cagney.
His irreverent, iconoclastic and often brash style quickly secured his reputation as a motor-mouth "shock jock" and he was eventually given his own mid-morning talk radio show.
Ryan went on to become a household name, with a daily audience of more than 300,000 listeners.