They wish to remain anonymous, only to say that they were "over the moon" about winning the jackpot, lottery officials say.
Despite the reduced payout and upfront tax costs, a lump sum payment is the most commonly chosen payout.
After taxes, the total payout comes to about $453 million between the two winners, or $250 million each.
That's because with the lump sum option, the $780.5 million payout would be subject to a 37% federal income tax, the highest bracket for top earners.
The odds of winning the Mega Millions jackpot are 1 in 302.5 million, according to MegaMillions.com.