Mary Ann Gates (née Maxwell; July 5, 1929 – June 10, 1994) was an American businesswoman, executive, civic activist, and school teacher. She was the first female president of King County's United Way, the first woman to chair the national United Way’s executive committee where she served most notably with IBM's CEO, John Opel, and the first woman on the First Interstate Bank of Washington's board of directors.

She served on the boards of various major corporations including the First Interstate Bank, Unigard Security Insurance Group, and Pacific Northwest Bell. She also served for 18 years (1975–1993) on the University of Washington's board of regents. She was the mother of Bill Gates, the co-founder of Microsoft.