Queensland's mystery lotto winner has been uncovered, a week after the record-breaking $150 million Powerball draw.

An Ipswich grandmother checked her ticket on Friday to discover she held one of the three division one winning entries and was about to become $50 million richer.

A Brisbane man and a Sydney dad each held the other two division one winning entries, claiming their $50 million prizes last week. However, the identity of the third winner had remained a mystery until Friday.

“I can’t believe it. I knew I wouldn’t be able to believe it until I called you but now I’m on the phone to you and I still don’t believe it," she told Golden Casket officials on Friday morning.