Players have been urged to check their numbers.
The jackpot winner matched all six main numbers to take home the “must be won” prize.
The winning Lotto numbers were 09, 11, 27, 44, 48, 52 and the bonus ball was 25.
One National Lottery ticket holder has matched all six main numbers, making them an instant millionaire.
Tonight's prize is the biggest jackpot of the year so far and had to be won following Wednesday's rollover of £8.4 million.
Wednesday’s estimated jackpot will now be £2 million.
No players matched all five numbers in Lotto HotPicks, which uses the same numbers as the Lotto draw.
Two players did win £13,000 each after they managed to match four numbers.
The winning Thunderball numbers were 05, 08, 10, 14, 20 and the Thunderball was 10.
No-one matched all five numbers plus the Thunderball to scoop the £500,000 top prize, but six ticket-holders matched all five regular numbers to win £5,000.
Andy Carter, senior winners’ adviser at Allwyn, operator of The National Lottery, said: “Wow, what a wonderful night of winning it’s been for Lotto players, as one lucky ticket-holder has won tonight’s special £15M ‘Must Be Won’ Lotto jackpot prize.
“Players are urged to check their tickets and to give us a call if they think they are tonight’s lucky winner.
"Playing any National Lottery game is more than just a chance to win; it's a way to contribute to something much bigger.
"Each week, players help generate around £30M for National Lottery-funded projects."
The largest amount ever to be won by a single ticket holder was £42 million in 1996.
