A Munster man won €6.6m in last Saturday's draw just 30 minutes after he topped up his online account.
The man claimed the prize today as part of a small family syndicate, and said he is still pinching himself in disbelief.
It is the sixth Lotto jackpot win since the National Lottery launched online play.
He said they plan to have a great Christmas, will clear the mortgage and bills, and then just see how they go.
He said: “I only recently began playing Lotto online as I was always forgetting to get my ticket in the shops.
"I opened the National Lottery App just half an hour before Saturday’s Lotto Draw and saw that there was only €3 in my account so I topped up, selected a Quick Pick and thought nothing else of it.”
The winner said he read on Sunday that an online player had won the Lotto but he didn’t think to check his numbers on the app until later on Sunday evening.
He said: “You never actually think it’s going to be you. I’m staring at this cheque with all these zeroes on it and I still cannot believe it.
"I checked my numbers when I saw the email come through and even at that stage I thought it would only be a couple of euros. We are going to take our time over the next few weeks and try to process this in our own heads.
"We are going to have a great Christmas, as normal with our family and then we’ll clear the mortgage and bills in the New Year. After that, we’ll just see how we go.”