Hope Hicks replaces Anthony Scaramucci, who was fired after 10 days.
She doesn't have a background in politics, but has been connected to the Trump family for the last five years.
And she's quietly worked her way up to being one of the president's closest allies - and one of his highest paid, on $180,000 (£140,000) a year.
So how did someone with such a low profile get one of the most important jobs in the US government?
Hope Hicks started her career in public relations, where Ivanka Trump's fashion company was one of her clients.