Nobody has claimed the €500,000 EuroMillions Plus prize won in Dublin.
The National Lottery office closed at 5.30pm, but the winner did not ring in so they will not get the prize.
It was the winning ticket in the EuroMillions Plus draw on October 1 this year and the Quick Pick ticket was bought at the Mace store in the Kilbarrack Shopping Centre in Dublin 5.
The winning numbers were: 09, 18, 26, 32 and 43.
National Lottery Spokesperson Robert Magee said it is very unusual that a ticket would go unclaimed.
He said: "Unfortunately in this case we had noone who came to claim the prize which was a EuroMillions Plus top prize of €500,000 that was won on the draw from October 1st.
"This winning ticket was sold in the Mace at Kilbarrack in Dublin 5.
"Any prize that is not claimed within 90 days of the draw become expired.
"In accordance with the licence to operate the National Lottery, they are used to promote the National Lottery and its gains so that therefore increases the funds raised for good causes."