The ticket was sold at the Market Store in Twizel for the December 28 draw.
"This is going to change our lives – what an amazing way to start the year," the winner said in a statament.
The winner is focused on how they can help others with the win, including plans to pay off the mortgages of close family members. They are also planning some overseas travel – something they never thought would be a possibility.
"I've travelled a little, but never thought I would ever have the chance to travel more. I have so many options now, and life will be so much easier."
Some of the $17.1m windfall will also be given to a "number of charities".
Lotto organisers had been considering hiring a private investigator to find the Twizel winner but the person came forward on their own accord.