After four months of waiting and speculation, the person who won a massive $US1.5-billion ($A2.1 billion) lottery payout has come forward to claim the prize, the local lottery agency in South Carolina has announced.

The draw was held in October and officials at the time said there was only one winning ticket. However, no one came forward to collect the prize, the largest ever single-winner payout – until now.

The winner has chosen to remain anonymous and will take a one-time payment of $US877,784,124 ($A1.2 billion).

The state will get $US61 million ($A86 million) in income taxes.

“The winner marvels at how every decision made that day brought the winner to the store, at that very moment, to make the Quick Pick Mega Millions lottery ticket purchase,” the lottery agency said in a statement.

“The winner even allowed a fellow customer to make a Mega Millions lottery ticket purchase in front of the winner while in line at the store. A simple act of kindness led to an amazing outcome.”