The 29-year-old is considered a key ally and close confident of the US president
White House communications director Hope Hicks is resigning, after three years as a central figure in both the Trump campaign and administration.
In early 2015, Ms Hicks was appointed as press secretary for Donald Trump's then potential presidential campaign
After the election, she was appointed as White House director of strategic communications - before being promoted to communications director in August 2017 following the short tenure of Anthony Scaramucci in the role.
While considered a key ally and close confident of the US president, Ms Hicks had also become engulfed in some of the controversies that have hit the White House in the year since Trump took office.
Earlier this week, she appeared before a lengthy closed session of the House Intelligence Committee - one of several committees investigating alleged Russian meddling in the 2016 election.
While the testimony was not made public, The New York Times reported that the 29-year-old told lawmakers that her work "occasionally required her to tell white lies" - but also insisted "that she had not lied about matters material to the investigations into Russia’s interference in the 2016 presidential election and possible links to Trump associates".
US media yesterday reported that Ms Hicks was stepping down from her role in the administration, and that was later confirmed by the White House.
There was no indication that her resignation and committee appearance were related.
In a statement quoted by US media, Ms Hicks said: “There are no words to adequately express my gratitude to President Trump. I wish the President and his administration the very best as he continues to lead our country.”
President Trump praised his outgoing senior aide, saying: “Hope is outstanding and has done great work for the last three years. 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."
He added that he was sure he would work together with Ms Hicks again in the future.
The resignation is not effective immediately, and Ms Hicks is instead set to leave her role in the coming weeks.