Thomas Stewart Udall (born May 18, 1948) is an American diplomat, lawyer, and politician serving as the United States Ambassador to New Zealand and Samoa. As a member of the Democratic Party, Udall served as a United States senator for New Mexico from 2009 to 2021. He also served as the U.S. Representative for New Mexico's 3rd congressional district from 1999 to 2009 and was the Attorney General of New Mexico from 1991 to 1999.