Hope Hicks, a long-serving adviser to Donald Trump, has quit her role as White House communications director.
The 29-year-old said she wanted to leave to explore opportunities outside Washington, having worked with Mr Trump as an aide throughout his presidential campaign and before that at The Trump Organisation.
"I wish the President and his administration the very best as he continues to lead our country," she said.
Ms Hicks only got the communications director job in Augustand was the youngest person to ever be appointed to the role, with the president describing her as "a little shy, but really, really talented".
"Hope is outstanding and has done great work for the last three years," the president said on Wednesday.
"She is as smart and thoughtful as they come, a truly great person. I will miss having her by my side but when she approached me about pursuing other opportunities, I totally understood.
"I am sure we will work together again in the future."
The announcement comes just a day after the former model spent eight hours testifying before the House Intelligence Committee over the ongoing investigation into alleged Russian interference in the 2016 election.
According to The New York Times, Ms Hicks admitted to the panel that she sometimes told "white lies" for the president, but denied lying about anything relevant to the Russia probe.
Her departure date is expected to be within the next few weeks, and leaves Mr Trump searching for a fifth communications director in little more than a year.
Ms Hicks has lasted the longest of the four: Sean Spicer lasted just 45 days, Mike Dubke was in the job for 88 days, and Anthony Scaramucci for less than a fortnight.
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She has not revealed what her next role will be.