The winning ticket for the €12.7m Lotto jackpot was sold in Co Kilkenny.
The winning numbers were 4, 14, 20, 23, 27, 37 with the bonus number of 39. The ticket was a Quick Pick.
The win is the 12th largest Lotto jackpot winner in the history of the game.
The ticket holder has yet to make contact with the National Lottery.
The store where the ticket was sold will be named in the coming days.
The National Lottery has advised the winner "to try their best to remain calm and be sure to sign the back of the ticket and keep it in a safe place".
The winners can contact the National Lottery prize claims team on 1800 666 222 or email claims@lottery.ie.
