No one has yet come forward to claim their £63.8 million share of the EuroMillions jackpot, a National Lottery spokeswoman said.
A UK ticketholder was one of two jackpot winners in Friday night's draw, with the other being with a ticket bought in Belgium.
The haul puts the lucky winner on a par with other multi-million-pound jackpot winners including Colin and Chris Weir, from Largs in North Ayrshire, who won £161 million last July.
Other big winners include a ticketholder who banked £113,019,926 in October 2010 but decided not to go public, and Dave Dawes and wife Angela, from Wisbech, Cambridgeshire, who claimed £101,203,600 last October.
Friday night's massive pot came about because of a double-rollover - last Friday six people won £266,505.80 each after matching five main numbers and one lucky star, but no one matched all seven to claim the £106 million jackpot.
The spokeswoman said: "Lady Luck is clearly shining down on the UK once again with another big EuroMillions win this year - the sixth jackpot win this year.
"We're absolutely delighted that a UK ticketholder has scooped a £63.8 million share of this massive jackpot, alongside one ticketholder in Belgium.
"We've got the Champagne on ice and look forward to welcoming the ticketholder into the National Lottery millionaires' club."
The exact amount won by the UK ticketholder was £63,837,543.60.