The winner matched all five main numbers and both the Lucky Stars to scoop the jackpot, which had been capped after a series of rollovers.
It is not yet known whether the ticket belongs to an individual or syndicate, or where they come from in the UK.
The winning Euromillions numbers were 17, 19, 38, 42 and 45, and the Lucky Stars were 9 and 10.
The exact amount to be claimed is £161,653,000.
A National Lottery spokesman said “This is amazing news – we are absolutely delighted that a UK ticket holder has scooped the entire 185 million euro jackpot, which at the current exchange rate is a massive £161m.
“This is the biggest winner this country and Europe has ever seen and follows hot on the heels of the anonymous ticket-holder who last October scooped £113m.
“In addition, two UK ticket holders in the next prize level down won £1.7m for matching five main numbers and one Lucky Star.
“We’ve got the champagne on ice and look forward to welcoming the ticket holders into the National Lottery millionaires’ club.”
No details were revealed of last October’s Euromillions winner and it is not known whether it was an individual or a syndicate.
Perhaps some of the winners might like to buy Greece with their winnings.