The claim window for a €1m jackpot has expired.
The National Lottery had issued a final plea to all players in Cork to check their tickets.
The Euromillions prize was won on February 23, in a Quick Pick ticket sold at the Eason Store in the Wilton Shopping Centre.
But the company has confirmed nobody came forward.
It says the prize will instead be used to promote the National Lottery - and help raise funds for good causes.