Mary Lea Trump (born May 3, 1965) is an American psychologist and writer. A niece of US president-elect Donald Trump, she has been critical of him. Her 2020 book about him and the family, Too Much and Never Enough, sold nearly one million copies on the day of its release. Two further books followed, The Reckoning (2021) and Who Could Ever Love You (2024).

In September 2020, Mary Trump sued her uncle Donald, aunt Maryanne, and the estate of her late uncle Robert, claiming that they defrauded her of tens of millions of dollars from her interests in her grandfather Fred Trump's real-estate portfolio. The lawsuit was dismissed in November 2022. Donald Trump sued Mary for at least $100 million in September 2021 for providing The New York Times with financial documents which was used as a source for a 2018 exposé about his wealth and the family's finances.