The ex-chairman and founder of Fox News Roger Ailes has died aged 77, his family says.
A statement from his wife Elizabeth said she was "profoundly sad and heartbroken", calling him a "patriot".
Mr Ailes ran Fox News for two decades and is credited with transforming it into arguably the most powerful voice in conservative media.
But he stepped down last year after a number of female employees accused him of sexual harassment.
At the time he said he was resigning because he had become a "distraction".
Mrs Ailes' statement said: "During a career that stretched over more than five decades, his work in entertainment, in politics, and in news affected the lives of many millions.
"And so even as we mourn his death, we celebrate his life."
The cause of his death has not been made public but CNN said he suffered a fall last week before slipping in to a coma, citing a family friend.
Rupert Murdoch, the head of Fox News' parent company 21st Century Fox, said Mr Ailes played a "huge role in shaping America's media over the last thirty years.
"Roger was a great patriot who never ceased fighting for his beliefs," he added.
Born in Warren, Ohio, his big break came in 1967 when Richard Nixon appeared as a guest on a talk show he was working on, persuading the future US president about the power of television.
He played a role in Mr Nixon's successful campaign, as well as for other Republican presidents Ronald Reagan and George Bush Snr.
Mr Ailes became the founding boss of Fox News in 1996, turning it into a profits and ratings powerhouse.
It soon became a favourite of right-wing viewers, outpacing liberal-leaning rivals like CNN.
The channel used the slogan "fair and balanced", but its critics saw it as anything but, accusing it of bias and of favouring the Republican Party.
Such was his influence, his biographer Gabriel Sherman quoted him as saying "I want to elect the next president" to a group of Fox executives at a 2010 meeting.
After leaving the company he reportedly helped Donald Trump prepare for the debates during his presidential campaign.
It would be hard to overstate the impact of Roger Ailes on American politics and culture over the past two decades.
As his bête noire the New York Times put it last year, he was kingmaker in a democracy that is meant to be king-proof, courted by presidential candidates and a confidante of Donald Trump.
Indeed, Trump's election owes a huge debt to the crusading, aggressive, and often conspiratorial agenda of Ailes' network.
Yet last summer he left amid huge controversy, earning tens of millions of dollars in a payout after allegations of sexual harassment were launched against him by former employees.
Ailes always denied the allegations against him. His death denies the rest of us the chance to hear his side of that particularly salacious story.