US President Donald Trump announced the switch on Twitter after a trip to New York, on which he was accompanied by Priebus, who has been under fire for weeks.
US President Donald Trump on Friday ousted his beleaguered chief of staff Reince Priebus, replacing him with retired Marine Corps general and current Homeland Security Secretary John Kelly.
Priebus has been under fire for weeks, seeing one White House ally after another resign or leave, culminating in the recent departure of press secretary Sean Spicer.
His exit appeared inevitable when Trump did not intervene as his new communications director Anthony Scaramucci publicly described Priebus as a "paranoid schizophrenic."
Trump announced the switch on Twitter after a trip to New York, on which he was accompanied by Priebus.
"I am pleased to inform you that I have just named General/Secretary John F Kelly as White House Chief of Staff," Trump said.
"He is a Great American... and a Great Leader. John has also done a spectacular job at Homeland Security. He has been a true star of my Administration."
TRT World's Jon Brain reports.
Kelly's Department of Homeland Security is responsible for enforcing border security and has taken a tough line on immigrants inside the United States.
The move likely signals a greater focus on law and order issues and will put further strain on relations between Trump and the Republican establishment.
Both Priebus and Spicer were part of the Republican National Committee, and the bridge that linked the party to Trump.
"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!" Trump said in a tweet.