CNN Chairman and CEO Chris Licht revealed the decision to Stelter on Wednesday, NPR reported.
Reportedly, Licht has been trying to return CNN to its more mainstream and newsgathering sources.
Stelter, along with his colleague, media reporter Oliver Darcy, have been among the network's most partisan talent.
The news comes after new Warner Bros. Discovery CEO David Zaslav has said CNN will be renewing its focus on journalism, signaling the network could soon return to its straight-news roots of previous decades.
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John Malone, the prominent shareholder of the integrated media company, previously told CNBC that he wished "real journalists" at the new CNN.
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Stelter, 36, who has hosted "Reliable Sources" for nine years, told NPR that he's grateful for the show.
"Reliable Sources" is the longest-running show on CNN, having celebrated its 39th anniversary in March. The show's last edition will be Aug. 21, a CNN spokesman told The New York Times.
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During the Trump presidency and after, Stelter and Darcy moved the network's nonpartisan media criticism to one closely aligned to the Democratic Party.
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Fox News reported that Stelter usually downplayed or ignored awkward stories about liberal media while focusing on conservative outlets for "disinformation."
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On air, Stelter frequently cited the Big Lie about Trump's contest of the 2020 election, a slogan that Licht has banned because it originated with the Democratic Party.
Stelter and Darcy shifted from being media critics to concentrating their attacks primarily on Trump and media that appeared to be aligned with him, including Fox News, Newsmax, OANN, and other outlets.
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The duo were the first to call for Trump's de-platform from Twitter, which they accomplished after Trump left office.
In 2021, Stelter and Darcy led attempts to have conservative news channels like Fox News and Newsmax de-platformed from cable systems.
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Conservatives called their efforts nothing short of censorship.
"We appreciate his [Stelter's] contributions to the network and wish him well as he embarks on new endeavors," the spokesman told the Times.
Stelter has been slammed by ex-President Trump's supporters for his partisan coverage of the former chief executive. The host routinely shares anti-Trump posts on his Twitter feed.
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A former Times media reporter, Stelter started blogging about cable news as a student.
"Stelter came to CNN from The New York Times as the nation's top media reporter. He departs CNN an impeccable broadcaster," said Amy Entelis, CNN's executive vice president for talent and content development, NPR reported.
"We are proud of what Brian and his team accomplished over the years, and we're confident their impact and influence will long outlive the show."