US President Donald Trump has named General John Kelly, who currently heads the Department of Homeland Security, as his next chief of staff.
I would like to thank Reince Priebus for his service and dedication to his country. We accomplished a lot together and I am proud of him!— Donald J. Trump (@realDonaldTrump) July 28, 2017
The announcement, made on Twitter on Friday afternoon, removes Reince Priebus from the role.
The embattled former chief of staff had faced pressure since being named as a possible leaker by Mr Trump's newly appointed director of communication.
Mr Preibus reportedly resigned on Thursday.
Reacting after the announcement, he said he would remain a strong supporter of President Trump's agenda and policies.
Anthony Scaramucci, who was appointed communications director one week ago, had accused Mr Priebus of leaking to the press in a tweet that he quickly deleted.
He also phoned a reporter to unleash a profanity-filled rant against Mr Priebus, whom he called a "paranoid schizophrenic".
Gen Kelly is a retired general who has become the face of border security.
In a series of tweets just before 5pm local time on Friday, the president praised the former Marine Corp general as a "great American" and a "great leader".
"John has done a spectacular job at Homeland Security. He has been a true star of my administration," said the president.
He will start work on Monday, a White House spokesperson says.
In a third tweet, President Trump praised the outgoing chief of staff, who had previously worked as the chairman of the Republican National Committee (RNC).
"I would like to thank Reince Priebus for his service and dedication to his country. We accomplished a lot together and I am proud of him," he said.
In his previous role as RNC chairman, he acted as a bridge between the Republican nominee and a party establishment that was often uncomfortable with its own presidential standard-bearer.