Nauert's nomination had been rumoured for weeks, and she had started handing over some of her responsibilities as spokeswoman to her deputy, Robert Palladino.
Early in her career, Nauert worked as a health insurance consultant, according to the State Department, which says she studied at Mount Vernon Seminary and College, a private women's college in Washington DC, and Columbia University's journalism school.
Nauert speaks as U.S. Secretary of State Mike Pompeo dialogues with reporters in his plane while flying from Panama to Mexico, Oct. 18.
When Trump named her as his to become ambassador to the United Nations, it came as a surprise to many.
When she announced her decision to step down the president called her a "very special person" and said she had told him some months before that she wanted to take some time off. Officials at the White House at times viewed Haley with skepticism, in part over her willingness to publicly disagree with the president.
In addition to that role, Ms Nauert was appointed acting undersecretary for public diplomacy and public affairs in March this year.More news: Trump's China auto tariffs claim sows confusion
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Nauert will probably be pressed on her qualifications by Senate Democrats and could face a contentious confirmation hearing, but needs only a simple majority vote to be elevated to the role.
Nauert's appointment was first reported by Bloomberg.
It was unclear whether the United Nations ambassador post would remain part of the Cabinet, as it has been under Ms Haley, and there have been internal discussions about not having it remain a Cabinet-level position, one White House official said. She had no government or foreign policy experience prior to joining the Trump Administration.
Trump has been known to change course on staffing decisions in the past.
The president considered Nauert for the position among a list of potential nominees that included former White House aide Dina Powell and ambassador to Germany Richard Grenell.
She was a popular anchor on the Fox News show Fox and Friends, which Mr Trump was said to watch.