According to Nielsen Media Research, an average of 84 million people watched the debate on one of the networks that carried it live from New York's Hofstra University on Monday. That figure alone is sufficient to break the old record of 80.6 million viewers set during a 1980 debate between Ronald Reagan and Jimmy Carter.
The total audience for Monday's event grows even larger when the millions of online livestream viewers are factored in -- as well as untold others on CSPAN, which is not measured.
Another sector of the audience not counted are those who watched at bars, airports, restaurants and businesses.
All told, the true number of viewers is almost certainly higher than 85 million and likely surpasses 90 million.
NBC notched the biggest audience, 18 million, possibly because network anchor Lester Holt moderated the first debate. ABC was second (13.5 million), followed by CBS (12.1), Fox News (11.4), CNN (9.9), Fox (5.5), MSNBC (4.9), Univision (2.5) and Telemundo (1.8).
YouTube estimated various live feeds totaled 2.5 million people. That does not include the hundreds of news sites that had their own streaming video sources.
"In terms of the social nature of the debate, there were 17.1 million Twitter interactions from 2.7 million people in the U.S. related to the "Presidential Debate" on Monday," Nielsen said in a statement.
Monday's audience was right around where industry executives expected it to be, between 80 and 100 million.
There are an estimated 115.6 million U.S. households with at least one television.
The next debate between Clinton and Trump is scheduled for Oct. 9 at Washington University in St. Louis. and will be moderated by ABC News' Martha Raddatz and CNN's Anderson Cooper.