Episodes of Strictly Come Dancing and The X Factor helped make Sunday's TV audience the biggest Sunday night audience for nearly 20 years.
An average total of 28 million people switched on their TV between 1800 and 2230, Barb figures show.
It is the biggest Sunday night audience on record since 1992, when current research methods began.
And the figure is likely to increase further once recorded viewing figures are added this week.
The bumper ratings were helped by the 17.2m people who saw former painter and decorator Matt Cardle win this year's X Factor on ITV1.
An average of 11.6m viewers also tuned in to watch the Strictly Come Dancing semi-final on BBC One.
Those who did so saw psychologist Pamela Stephenson, TV host Matt Baker and former EastEnder Kara Tointon advance to next weekend's final round.
The overall ratings were boosted by editions of Countryfile, Inspector George Gently and Antiques Roadshow on BBC One.
Piers Morgan's interview with Sir Elton John on ITV1 and Five's screening of Dirty Dancing also added to the record-breaking total.
At one point, between 2045 and 2100 GMT, an average of 31.9m people were watching a television programme.
"It's remarkable to get that many people watching TV," said David Bunker, head of research at BBC Vision.
"It's as much about all channels offering something for all audiences. Antiques Roadshow and The X Factor are at two ends of the spectrum - hence you get massive audiences."
"An audience of almost 20 million is a phenomenal achievement for any channel in the modern digital age," said Peter Fincham, ITV's director of television.
The overnight figures come ahead of a final consolidated figure that includes people who watch that day's programmes in the week or so afterwards, via hard disk recorders like Sky+ or other methods.