The recipient could choose the $521 million annuity payment option, doled out over the course of 29 years.
They appear on a single ticket sold at a Lukoil gas station in Riverdale, New Jersey, the New Jersey Lottery said on Twitter.
The woman's ticket matched all six numbers.
The cash option would pay United States $317 million.
The location where the winning ticket was sold was not disclosed.
Mega Millions is the nation's 10th-largest lottery jackpot. Mega Millions tickets are sold in 43 states plus the District of Columbia and the U.S. Virgin Islands.