Dominion Voting Systems v. Fox News Network (colloquially Dominion v. Fox) was a U.S. defamation lawsuit filed in March 2021 by Dominion Voting Systems against Fox News Channel and its corporate parent Fox Corporation. Dominion's complaint sought US$1.6 billion in damages, alleging several Fox programs had broadcast false statements that Dominion's voting machines had been rigged to steal the 2020 United States presidential election from then-president Donald Trump. Fox News argued that it was reporting "pure opinion" regarding what others were saying which, if true, would be protected by the First Amendment to the Constitution.

Dominion focused on allegations made between November 2020 and January 2021 by hosts Maria Bartiromo, Tucker Carlson, Lou Dobbs, Sean Hannity, and Jeanine Pirro. Guests who often appeared with these hosts included Trump attorneys Rudy Giuliani and Sidney Powell, both of whom have also been sued individually by Dominion in federal court. During pre-trial discovery, Fox News' internal communications were released, indicating that prominent hosts and top executives were aware the network was reporting false statements but continued doing so to retain viewers for financial reasons.

In a summary judgment on March 31, 2023, Delaware Superior Court judge Eric M. Davis ruled that none of the disputed statements Fox News made about Dominion were true and ordered a trial to determine if the network had acted with actual malice. Several prominent Fox News personalities and senior executives were expected to testify at trial. On April 18, as opening statements were about to begin, the judge announced that the parties had reached a settlement. Fox News agreed to pay Dominion $787.5 million and acknowledged the court's earlier ruling that Fox had broadcast false statements about Dominion. The settlement did not require Fox News to apologize. It is the largest known media settlement for defamation in U.S. history. Later that month, Tucker Carlson was fired from hosting Tucker Carlson Tonight, one of cable's highest-rated news shows, in response to the lawsuit's allegations of a toxic work environment on the show's set.

After Trump's defeat in the 2020 presidential election, Fox News host Jeanine Pirro promoted baseless allegations on her program that Dominion and its competitor Smartmatic had conspired to rig the election against Trump. Hosts Lou Dobbs and Maria Bartiromo also promoted the allegations on their programs on sister network Fox Business. In December 2020, Smartmatic sent a letter to Fox News demanding retractions and threatening legal action, specifying that retractions "must be published on multiple occasions" so as to "match the attention and audience targeted with the original defamatory publications." Days later, each of the three programs aired the same three-minute video segment consisting of an interview with an election technology expert who refuted the allegations promoted by the hosts, responding to questions from an unseen and unidentified man. None of the three hosts personally issued retractions. Smartmatic filed a $2.7 billion defamation suit against the network, the three hosts, Trump campaign attorney Sidney Powell and Trump personal attorney Rudy Giuliani in February 2021. In an April 2021 court brief seeking dismissal of the suit, Fox attorney Paul Clement argued that the network was simply "reporting allegations made by a sitting President and his lawyers." The Smartmatic's lawsuit accusing Fox of defamation is still pending as of September 2023.

In December 2020, Dominion sent a similar letter demanding retractions to Trump attorney Sidney Powell, who had promoted the allegations on Fox programs. On March 26, 2021, Dominion filed a $1.6 billion defamation lawsuit against Fox News, alleging that Fox and some of its pundits spread conspiracy theories about Dominion, and allowed guests to make false statements about the company. On May 18, 2021, Fox filed a motion to dismiss the lawsuit, asserting a First Amendment right "to inform the public about newsworthy allegations of paramount public concern." The motion to dismiss was denied on December 16, 2021 by Davis.

Specifically, Dominion focused on allegations made between November 2020 and January 2021 by Maria Bartiromo on her show Sunday Morning Futures with Maria Bartiromo and Fox & Friends; by Carlson on Tucker Carlson Tonight; by Dobbs on Lou Dobbs Tonight and on Dobbs's Twitter account; by Hannity on Hannity; and by Pirro on Justice with Judge Jeanine. Guests who often appeared during these segments included Rudy Giuliani and Sidney Powell. Dominion was represented by law firms Clare Locke, Farnan LLP, and Susman Godfrey. Fox retained Clement & Murphy, DLA Piper, Ellis George Cipollone, Lehotsky Keller, Richards Layton & Finger, and Winston & Strawn. In addition to asserting First Amendment protection, Fox News cited the landmark 1964 Supreme Court decision New York Times Co. v. Sullivan, which found a public figure seeking to prove defamation must demonstrate that a publisher acted with actual malice: that they knew what they published was false or recklessly disregarded whether it might be false.

In June 2022, Davis again declined to dismiss the Dominion suit against Fox News, and also allowed Dominion to sue the network's corporate parent, Fox Corporation. Davis ruled that Fox Corporation chairman Rupert Murdoch and CEO Lachlan Murdoch may have acted with actual malice because there was a reasonable inference they "either knew Dominion had not manipulated the election or at least recklessly disregarded the truth when they allegedly caused Fox News to propagate its claims about Dominion." He noted a report that Rupert Murdoch spoke with Trump a few days after the election and informed him that he had lost.

The New York Times reported in December 2022 that Dominion had acquired communications between Fox News executives and hosts, and between a Fox Corporation employee and the Trump White House, showing they knew that what the network was reporting was untrue. Dominion attorneys said hosts Sean Hannity and Tucker Carlson, and Fox executives, attested to this in sworn depositions. In November 2020, Sidney Powell appeared on Hannity and asserted Dominion machines had been rigged, but Sean Hannity said in his deposition, "I did not believe it for one second." A February 2023 Dominion court filing showed Fox News primetime hosts messaging each other to insult and mock Trump advisers, indicating the hosts knew the allegations made by Powell and Giuliani were false. Rupert Murdoch messaged that Trump's voter fraud claims were "really crazy stuff", telling Fox News CEO Suzanne Scott that it was "terrible stuff damaging everybody, I fear." As a January 2021 Georgia runoff election approached that would determine party control of the Senate, Murdoch told Scott, "Trump will concede eventually and we should concentrate on Georgia, helping any way we can."