The first Hillary Clinton vs. Donald Trump presidential debate was watched by 84 million people, breaking a previous TV record set 36 years ago.
In 1980, Jimmy Carter and Ronald Reagan’s debate drew 80.6 million viewers.
The viewing figures only count those who watched the debate on the 13 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.
Donald Trump told supporters on September 27 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,” the Republican said.
In 2015, the NFL’s Super Bowl won the biggest 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 October 9 and 19 – before the election on November 8.
On October 9, Hillary Clinton and Donald 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.