More than 11 million viewers watched the Duke and Duchess of Sussex’s interview on ITV.
The broadcaster snapped up the rights to the programme in a deal reported to have cost around £1 million.
The CBS primetime special with Oprah Winfrey aired first on Sunday in the US, where it reached an estimated 17.1 million viewers.
ITV said the broadcast was viewed by “more than half of people watching television across the UK at that time”.
Oprah With Meghan And Harry had an average audience of 11.1 million and 54% share between 9pm and 11pm.
It was watched by a peak audience of 12.4 million viewers on Monday night.
“This was ITV’s biggest peak audience since the 2019 Rugby World Cup final and the biggest on any channel (outside Government, pandemic-related announcements) since the Strictly Come Dancing final on BBC One in December,” ITV said.
The Strictly final, won by Bill Bailey last year, attracted an average of 11.6 million viewers and a peak of 13.2 million, according to overnight ratings.
The Panorama interview with Diana, Princess of Wales, broadcast on BBC One in 1995, had overnight ratings of 21.1 million.
The Prince of Wales’s interview with Jonathan Dimbleby, broadcast on ITV in 1994, in which Charles admitted he had committed adultery, had overnight ratings of 12.7 million.
ITV also said that 2.2 million streamed the Harry and Meghan interview, which made headlines around the world, on ITV Hub.
It said the interview was a hit among young viewers, with four out of five viewers aged 16 to 34 tuning in.
The figures make it the biggest 16-to-34 TV audience for overnight viewing, outside of news programming, since I’m A Celebrity… Get Me Out Of Here! last year, ITV said.
Earlier this year, the final of The Masked Singer was watched by an average audience of 8.6 million viewers.
The audience peaked at 10.6 million during the programme, which saw Joss Stone crowned as the champion after the singer was revealed to be Sausage.