The National Lottery has confirmed the winning ticket for the €4.5m Christmas Eve jackpot was sold in Co Cavan.
The total value of the Quick Pick ticket is €4,577,663.
The winning ticket was bought in the SuperValu on Main Street, Bailieborough in Co. Cavan on the day of the draw.
The winning numbers were 8, 10, 11, 16, 40, 42 and the bonus number 38.
The National Lottery advised everyone to check their tickets, and said its offices would reopen on Thursday.
The lucky ticketholder is advised to immediately sign the back of the ticket and contact the National Lottery Prize Claims Team on 01 836 4444.