Mary Williams may refer to:
Mary Williams (caricaturist) (1869–1960), American caricaturist who used the pseudonym Kate Carew
Mary Williams (The Young and the Restless), fictional television character
Mary Williams, former Chief Secretary of the Isle of Man
Mary Williams (Wisconsin politician) (born 1949), member of the Wisconsin State Assembly
Mary Alice Williams (born 1949), former television anchor
Mary Burrus Williams (born 1941), co-author of historical novels under the pen name Bronwyn Williams
Mary Elizabeth Williams, American writer and commentator
Mary Ellen Coster Williams (born 1953), United States Court of Federal Claims judge
Mary Lou Williams (1910–1981), American jazz pianist, composer, and arranger
Mary Luana Williams, American social activist and adopted daughter of Jane Fonda
Mary Wilhelmine Williams (1878–1944), historian
Mary Williams, character in Another Man, Another Chance