Morris King Udall (June 15, 1922 – December 12, 1998) was an American attorney and Democratic politician who served as a U.S. representative from Arizona from May 2, 1961, to May 4, 1991. He was a leading contender for the 1976 Democratic presidential nomination, but ultimately lost to eventual president, Jimmy Carter. Udall was noted by many for his independent and liberal views.

In 1961, Udall won a special election to succeed his brother, Stewart Udall, as the congressman for Arizona's 2nd congressional district. In Congress, Udall became a prominent and popular figure for his independent ways, his leading role in the conservation and environmental protection movements, his key role in reforming Congress and political campaigns, and his pioneering role in opposing the Vietnam War.

Udall sought the Democratic Party nomination in the 1976 presidential election, but was defeated by Jimmy Carter. He supported Ted Kennedy's strong challenge to Carter in the 1980 Democratic primary, and delivered the keynote address at the 1980 Democratic National Convention.

Udall served as chairman of the House Interior Committee from 1977 to 1991. Diagnosed with Parkinson's disease in 1980, he resigned from Congress in 1991 as the effects of the disease worsened. He died in 1998. His son, Mark Udall, represented Colorado in the United States Senate from 2009 to 2015, and his nephew Tom Udall served as a United States Senator from New Mexico from 2009 to 2021. Both also served multiple terms in the U.S. House of Representatives.