"I am pleased to inform you that I have just named General/Secretary John F Kelly as White House Chief of Staff. He is a Great American," Trump tweeted, "and a Great Leader. John has also done a spectacular job at Homeland Security. He has been a true star of my Administration.
CNN reported Priebus resigned privately Thursday.
"It has been one of the greatest honors of my life to serve this president and our country," Priebus said in a statement. "I want to thank the president for giving me this very special opportunity. I will continue to serve as a strong supporter of the Ppresident's agenda and policies. I can't think of a better person than General John Kelly to succeed me and I wish him God's blessings and great success."
Priebus' departure wasn't entirely unexpected. One day earlier, The New Yorker magazine published a profanity-laced interview with newly named White House communications director Anthony Scaramucci, who fueled rumors of discord with Priebus.
"Reince is a [expletive] paranoid schizophrenic, a paranoiac," Scaramucci said, suggesting Priebus and White House chief strategist Steve Bannon were behind White House leaks.
Prior to joining the Trump administration, Priebus was chairman of the Republican National Committee and Republican Party of Wisconsin.
"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 announcing Kelly's new role.