Trump Names Stephen Miller New Chief of Staff After GOP's Brutal Midterm Losses

President Trump is shaking up his inner circle after Republicans' brutal midterm election losses ... naming longtime loyalist Stephen Miller as his new White House chief of staff in a stunning move.

Trump announced the shocking change Friday on Truth Social, praising Miller as one of his "most trusted advisors" while thanking outgoing chief of staff Susie Wiles for doing an "outstanding job."

Miller takes over Monday, while Wiles moves to the "Trump Political Operation."

But there may be more to the shakeup ... Trump reportedly blamed Wiles for the GOP's election night disaster in front of others and has been furious with his team since Tuesday's losses.

POTUS also reportedly had been privately asking people what they thought about Miller taking over the job ... suggesting a major shakeup was already on his mind.

Wiles addressed her departure on social media Friday, calling her time as Trump's chief of staff the "honor of a lifetime" ... adding that while her role is changing, her commitment to Trump "never will."

The departure comes after a difficult year for Wiles, who was diagnosed with breast cancer in March. She continued working through treatment and announced in September she was cancer-free.

The shakeup puts one of Trump's most trusted allies -- and the architect of his controversial immigration policies -- in charge of the West Wing, days after Democrats dealt Republicans a major election defeat.

Miller has been in Trump's orbit since his first presidential campaign in 2016, serving throughout his first administration and becoming one of the most powerful figures of his second term.

Beyond immigration, he's helped drive Trump's crackdown on liberal institutions and has fiercely defended some of the president's most controversial moves ... including his ambitions involving Greenland.