Update: 12:30 a.m. ET Wednesday
Stewart closed Tuesday night's episode of The Daily Show with discussion of his pending departure.
"Seventeen years is the longest I have ever — in my life — held a job, by 16 years and five months," Stewart said. "The upshot there being, I am a terrible employee. ...
"We're still working out details, I'm up in September, I'm up around then, might be December, might be July ... I don't have any specific plans. Got a lotta ideas, I got a lot of things in my head. I'm gonna have dinner — on a school night! — with my family, who I have heard from multiple sources are lovely people.
"This show doesn't deserve an even slightly restless host, and neither do you. I don't think I'm going to miss on television every day — I'm gonna miss coming here every day ... I love the people here, they're the best. They're creative and collaborative and kind."
"It's been an absolute privilege. It's been the honor of my professional life."
Jon Stewart, the comedian who has become a highly influential figure in American politics, is leaving The Daily Show sometime this year.
Stewart let the news slip during this evening's taping of the show.
Fittingly, The A.V. Club, a real-news spin-off of The Onion, first reported the news and Comedy Central confirmed it, saying Stewart would step down "later this year."
"Jon has been at the heart of Comedy Central, championing and nurturing the best talent in the industry, in front of and behind the camera," Michele Ganeless, Comedy Central's president, said in a statement. "Through his unique voice and vision, The Daily Show has become a cultural touchstone for millions of fans and an unparalleled platform for political comedy that will endure for years to come. Jon will remain at the helm of 'The Daily Show' until later this year. He is a comic genius, generous with his time and talent, and will always be a part of the Comedy Central family."
The A.V. Club quoted audience members saying Stewart said he was "retiring."
Comedy Central's other towering figure of political satire, Stephen Colbert, ended his own run on The Colbert Report, last year.
Colbert is taking over for David Letterman in September.
Billed as "the most trusted name in fake news," Stewart has been hosting The Daily Show on Comedy Central in 1999. Despite its irreverence and its sometimes cutting humor, the show has attracted the most prominent of American political figures seeking to woo a younger demographic.
Everyone from Presidents Obama and Clinton to Gen. Colin Powell and Sen. John McCain have appeared on the show with Stewart.
In a recent Pew study, 12 percent of respondents said they had gotten political news from the program. That compares to 12 percent who answered USA Today and 10 percent who answered The Wall Street Journal.