The presidential debate between Hillary Clinton and Donald Trump was watched by 84 million people on US TV, breaking a previous record set 36 years ago.
Jimmy Carter and Ronald Reagan’s debate in 1980 drew 80.6 million viewers.
The viewing figures only count those who watched the debate on the 13 US TV channels that carried it live, meaning the true figure may be much higher.
Millions are also thought to have watched worldwide through online live streams or in bars and at parties.
The data provider Nielsen said that viewers stayed tuned through the 98-minute debate.
Mr Trump told supporters on Tuesday that he knew the debate would have “one of the largest audiences in the history of television” but he “took a deep breath” and “pretended I was talking to my family”.
“You just block it out,” he said.
In 2015 the NFL’s Super Bowl won the biggest US TV audience to date when 114.4 million people watched New England play Seattle.
There are two more presidential debates to come between the candidates – on 9 October and 19 October – before the election on 8 November.
On 9 October, Mrs Clinton and Mr Trump will have competition for the attention of the US; NFL teams the Green Bay Packers and the New York Giants will be playing at the same time as the second debate.
Overnight polls with small samples were split on who won the first televised debate on Monday, but more rigorous surveys are due in the coming days.
On Tuesday, Mrs Clinton said she felt the debate had highlighted important differences between her and Mr Trump.
“His demeanour, his temperament, his behaviour on the stage could be seen by everybody and people can draw their own conclusions,” she said.
“And I thought on several occasions he was making charges and claims that were demonstrably untrue – offering opinions that I think a lot of people would find offensive and off-putting.
“He can run his campaign and present himself however he chooses, but the real point is about temperament and fitness and qualification to hold the most important, hardest job in the world and I think people saw last night some very clear differences between us.”
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