"I will not seek reelection to Democratic leadership in the next Congress,'' Pelosi said in a speech on the House floor to a joint session. "For me, the hour has come for a new generation to lead the Democratic caucus that I so deeply respect.''
"Now we must move boldly into the future," she declared. "The hour has come for a new generation."
The House Speaker, who has led the Democrats in the lower house of Congress for 20 years, said she would continue to serve as representative for California's 12th District, which she has done since 1987.
In response, US President Joe Biden called Pelosi a "fervent defender of democracy," adding that the nation owed her a deep debt of gratitude.
"When I think of Nancy Pelosi, I think of dignity. History will note she is the most consequential Speaker of the House of Representatives in our history," he added.
The announcement comes a day after US media projected that the Republican Party would take control over the House with a narrow majority, bumping Pelosi from her role as Speaker when the new Congress takes office in January.
According to reports, the rest of Pelosi's "triumvirate" of Democratic Party leaders, House Majority Leader Steny Hoyer (D-MD) and Democratic Whip James Clyburn (D-SC), could also be preparing to step down. Pelosi and Clyburn are 82 years old, and Hoyer is 83.
"I do wish to remain at the leadership table,'' Clyburn told reporters earlier this week. "As to what capacity that will be, I will leave that up to our Democratic caucus."
Pelosi has led the House Democratic Caucus since 2003, and first became Speaker in 2007, after Democrats swept into majorities in both chambers. From 2011 until 2019, she served as Minority Leader as Republicans held a majority, and returned to the Speaker's seat in 2019.
Her announcement also comes as her husband, investor Paul Pelosi, is recovering from an attack at their San Francisco home last month. His alleged attacker, a Canadian citizen named David DePape, has been indicted by a federal grand jury on charges of assault and attempted kidnapping. DePape told police he had entered the Pelosis' home looking for the Speaker, but found her husband, and attacked him with a hammer, giving Paul a fractured skull and serious injuries to his hands and arms.