A UK-based ticketholder won nearly £41 million on last night's EuroMillions draw, Camelot said.
The winner scooped the rollover jackpot of £40,627,241.
A Camelot spokesman said: "This is fantastic news - we're absolutely delighted to have yet another huge EuroMillions win here in the UK.
"We have plenty of champagne on ice and look forward to welcoming the lucky ticketholder into The National Lottery millionaires' club.
"Over 2,800 people have become millionaires since The National Lottery began and, to date, our players have raised an amazing £27 billion and counting for National Lottery Good Causes."
No one has yet come forward to claim the prize.
The success is the seventh biggest UK lottery win. The record is held by Colin and Chris Weir, from Largs, Scotland, who won £161 million on EuroMillions last July.
The winning main EuroMillions numbers were: 02, 10, 22, 27 and 28, and the winning Lucky Star numbers were 06 and 08.