Maria E. Cantwell (born October 13, 1958) is the junior United States Senator from the state of Washington and is a member of the Democratic Party. Previously she served in Washington House of Representatives and one term as member of the United States House of Representatives from Washington's 1st congressional district. She is Washington's second female senator.

Cantwell and Debbie Stabenow of Michigan were the first women to defeat elected incumbent Senators in a general election. In 1992, Carol Moseley Braun had defeated incumbent Alan J. Dixon in the Democratic primary, and later that year Dianne Feinstein defeated appointed incumbent John F. Seymour in a special election; Kay Bailey Hutchison defeated appointed Senator Bob Krueger in a 1993 special election.

Cantwell was born in Indianapolis, Indiana. She was raised in a predominantly Irish neighborhood on the south side of Indianapolis. Her father, Paul F. Cantwell, served as county commissioner, city councilman, state legislator, and Chief of Staff for U.S. Representative Andrew Jacobs, Jr.. Her mother, Rose M., was an administrative assistant.