The National Lottery has confirmed that the winning ticket in the EuroMillions draw was sold in Munster.
A spokesperson said that the ticket was purchased in a retail outlet.
Jennifer Crowe of the National Lottery said the winner has yet to come forward.
"At this stage we don't know anything about the winner. We are appealing to all players in Munster to check their tickets carefully.
"If they are the winner stay calm sign the back of the ticket and make contact with the National Lottery claims team," Ms Crowe said.
The National Lottery said that it hopes to be able to announce the county where the ticket was sold and the retail outlet in the coming days.
It has sent its congratulations to the winner who now holds the title as the record holder of the highest ever win.
It said it always encourages winners to seek independent legal advice before collecting their cheque.
This is Ireland's 18th EuroMillions win since the draw began in 2004.
We need your consent to load this rte-player contentWe use rte-player to manage extra content that can set cookies on your device and collect data about your activity. Please review their details and accept them to load the content.Manage PreferencesNational Lottery spokesperson Emma Monaghan said it was all hands on deck last night after the news filtered through of the record-breaking win.
It is the highest possible amount that can be won on the EuroMillions - which is capped at €250 million - and eclipses the €175m win by the Naul Family syndicate in Dublin in 2019.
"It's great news for Irish players, we are the delighted for the winner," she said.
Speaking on RTÉ's Morning Ireland, she said it is an eye watering amount of money to win and no doubt has come as a huge shock to the winner.
Watch: People in Cork give their say on the EuroMillions win
Ms Monaghan said players have 90 days to claim the prize, but she hopes that the holder of the winning ticket comes forward before then.
"If at all possible, to stay calm, I know that might be easier said than done. Have a cup of tea and just let it sink in. Players do have 90 days to claim the prize. So I'm hoping that they will make contact before then."
The National Lottery said it is ready to guide the winner through the process once they are ready to come forward.
It added that it will be a few days before they will be able to confirm where in Ireland the shop that sold last night's winning ticket is.
The winning numbers are 13, 22, 23, 44, 49 - Lucky Stars 3 and 5.
Dolores McNamara was Ireland's first EuroMillions winner, collecting more than €115m in July 2005.
In June 2013, a Dublin player picked up more than €93m in a share of a jackpot worth over €187m, while in July 2020 an online player won €49.5m with a €2.50 ticket.
What to do with winnings?
When asked what they would do with the winnings, many in Dublin this morning said they would share their winnings with family.
"Sit back and do nothing for a while," is what one man said he would do, adding that he would help family and look to address world hunger.
"It might be hard to hide it, I might have a large car outside instead of the usual banger," he added.
One woman said that her priority if she won big would be making sure her loved ones were looked after.
"I would go on holiday and buy an apartment in Spain," another woman said, while a young man said that he would buy a house and "travel around Europe".
We need your consent to load this rte-player contentWe use rte-player to manage extra content that can set cookies on your device and collect data about your activity. Please review their details and accept them to load the content.Manage Preferences
One woman from Wicklow said she know exactly what she would do, because it is what her late husband would want her to do.
"There are so many elderly homeless and not through any fault of their own, and I would start up an organisation and then all these people would have homes," she said.
Others said they would wait and think about it before doing anything with it.
A man from Mullingar, Co Westmeath, said he would find it overwhelming, and would not want it at all.
"I dread it, believe it or not, life is good, our children are healthy we're healthy and to be honest I'd rather not win it. I would fear for our health or losing the run of themselves."
Additional reporting Sheila Naughton
