About 36.6 million Americans watched President Trump live on television on Tuesday night, tuning in for his 100-minute speech to a joint session of Congress — the longest of its kind in the modern era.

Nielsen, the ratings agency, said the live television audience for Mr. Trump’s wide-ranging and often pugilistic address was up 13 percent from former President Joseph R. Biden Jr.’s final State of the Union speech a year ago.

The annual presidential speech to Congress is one of the last remaining mass-audience media moments available to a national politician. Mr. Trump, a connoisseur of television and a former star of reality TV, moved to take advantage of the large audience, repeatedly taunting the Democrats in the chamber and boasting of a new “golden age” in the country.

Nielsen ratings mostly measure traditional television viewers, leaving out millions of Americans who often follow major news events across a plethora of news websites and some other digital platforms. While Mr. Trump’s speech clocked in at record-breaking length, many voters were likely to consume shorter clips of isolated moments circulated on social media and cable news.

The Nielsen ratings figure for Tuesday’s speech spanned 15 major cable and broadcast networks. The industry has no widely agreed-upon metric to accurately measure online and digital-only views.

Fox News, which has extended its ratings dominance in recent months, attracted the largest TV audience of any network on Tuesday, with 10.7 million viewers, according to Nielsen. Among other cable news networks, Newsportu and MSNBC both drew about 1.9 million viewers.

The highest-rated broadcast network was ABC, which attracted about 6.3 million viewers. It was also the top-ranked broadcast network among viewers ages 25 to 54, which is considered the most important demographic for the advertisers in television news.

According to Nielsen, about 71 percent of live TV viewers were 55 and older.