Updated at 7:50 p.m. ET
President Trump ended a week defined by White House staff turmoil when he named retired Marine Gen. John Kelly as his new chief of staff on Friday evening.
Trump made the announcement via Twitter.
"He is a Great American and a Great Leader," Trump said. "John has also done a spectacular job at Homeland Security. He has been a true star of my Administration."
Trump also tweeted his thanks to Reince Priebus, who had been his chief of staff since Inauguration Day.
"I would like to thank Reince Priebus for his service and dedication to his country," Trump said. "We accomplished a lot together and I am proud of him!"
Priebus served a scant 189 days as chief of staff, the shortest tenure in decades for someone in that post. In 2012, Trump, taking to Twitter, criticized President Obama for his "3 Chief of Staffs in less than 3 years."
The replacement of Priebus comes just a week after Sean Spicer, a Priebus ally, resigned as press secretary the same day Trump brought on Anthony Scaramucci as communications director.
On Wednesday, Scaramucci went on an expletive-laden rant to a reporter in which he called Priebus a "paranoid schizophrenic, a paranoiac."
In an interview with CNN, Priebus said, "This is not like a situation where there's a lot of ill will feelings."
"I think it was time to hit the reset button," he said. Pressed on the conversations he had with the president about his decision to leave, Priebus said, "The president is professional. Professional people don't discuss private conversations in public."
Priebus said only that the president "wanted to go in a different direction."
He praised the president and Kelly and declined to discuss the Scaramucci interview, saying, "I am not going to get into the mud."
"I resigned, and he accepted it," Priebus said, adding that he had tendered his resignation on Thursday after discussing it with the president for "a few days."
"I am always going to be a Trump fan. I am on Team Trump," he said.
White House press secretary Sarah Sanders said the decision to make a change "started with the president and Reince about two weeks ago, in terms of timing." She said it had nothing to do with Scaramucci.
Asked when Kelly was offered the chief of staff job, she said "They've been talking about it for a while."
House Speaker Paul Ryan, R-Wis., is a friend of Priebus' and released a statement following Trump's announcement.
"Reince Priebus has left it all out on the field, for our party and our country," Ryan said. "He has achieved so much, and he has done it all with class."
Ryan added that he was looking forward to working with Kelly as well.
Before taking over as secretary of homeland security, Kelly, 67, served in the top slot of the U.S. Southern Command, the Pentagon's area of responsibility focused on the Caribbean and South America, and notably Guantanamo Bay, Cuba.
Trump has shown an affinity for generals in his administration. Retired Gen. James Mattis is Trump's defense secretary, and Trump's first choice for national security adviser was retired Army Lt. Gen. Mike Flynn.
Kelly was confirmed with bipartisan support by the Senate, 88-11, on Inauguration Day. He had been leading DHS' recent surge in efforts to crackdown on illegal immigration — a core campaign promise by Trump.
On Friday afternoon, during a speech in Long Island, N.Y., Trump gave what now seem like foreshadowing remarks.
"I want to congratulate John Kelly, who has done an incredible job of secretary of homeland security," Trump said. "Incredible."
In a statement, Kelly said he is "honored" to be asked to serve as the chief of staff.
"I have been fortunate to have served my country for more than 45 years — first as a Marine and then as the Secretary of the Department of Homeland Security," he said.
However, Kelly has clashed with congressional Democrats in recent months because he has indicated that the Trump administration was unlikely to continue the Obama-era deferred action for childhood arrivals program that protects certain eligible youth from deportation if they were brought to the U.S. illegally by their parents. The retired general has told Democrats that it is Congress' responsibility to change immigration laws if they want to codify DACA.
Trump has yet to say who he plans to nominate to take Kelly's place atop the Department of Homeland Security. The Senate will have to vote to confirm whomever he chooses. The department said Friday in a statement that Kelly remains secretary until Monday, July 31. Then, Deputy Secretary Elaine Duke becomes the acting secretary.
NPR's Susan Davis contributed to this report.