Canberrans have been urged to check their Lotto tickets. Someone who bought a ticket in Curtin Newsagency and Post Office stands to win $1,441,433.03.
Because the ticket was unregistered, the organisers have no way of contacting the lucky winner.
The mystery player held one of the seven division one winning entries in the draw on Saturday.
The owner of the shop, Thuy Nguyen, said the winning entry was "momentous".
"We're a family-run business and we're absolutely thrilled to hear our store had sold a division one winning entry in the weekend's Saturday Lotto draw," she told the Lotto company, the Lott.
"We wish our mystery winner a big congratulations on this life-changing victory! We sincerely hope this brings great joy and prosperity to your life.
"May your newfound fortune open doors to a future filled with happiness and fulfilment.
"Being an outlet that has sold seven division one winning entries is a source of immense pride for us.
"It reaffirms our commitment to providing our customers with a chance at life-altering moments.
"We will be planning special promotions and discounts at our shop this week to celebrate.
"We want our customers to share in the excitement and feel the joy of this significant accomplishment."
Lott spokesperson Anna Hobdell said: "It's most likely our latest ACT winner has woken up today, gone about their usual morning routine and headed off to work with no idea they've won $1.4 million in the weekend's Saturday Lotto draw."
"We're urging all players who purchased a Saturday Lotto ticket from Curtin Newsagency & Post Office to check their tickets as soon as possible," she said.
"Winning tickets can often be found in wallets, handbags, fridge doors or car gloveboxes. Be sure to check anywhere or everywhere because the winner could be you.
"If you discover you are holding the winning ticket, contact The Lott on 131 868 to begin the process of claiming your prize."
