Thomas Mark Barrett (born December 8, 1953) is an American diplomat and politician who has served as the United States ambassador to Luxembourg since 2022. He previously served as the 44th mayor of Milwaukee, Wisconsin from 2004 until 2021. A member of the Democratic Party, he was previously elected to the Wisconsin State Assembly (1984–1989), Wisconsin Senate (1989–1993) and U.S. House of Representatives (1993–2003). On April 6, 2004, Milwaukee elected Tom Barrett as its 40th mayor. He won reelection in 2008, 2012, 2016 and 2020. When he left office, Barrett was the longest-serving current mayor of one of the 50 largest cities in the United States. Early life, education and early career Barrett is the oldest son of Gertrude Virginia (of German and English descent) and Thomas J. Barrett (of Irish descent). His father was a World War II veteran who was awarded the Distinguished Flying Cross in 1944 for 30 missions over Germany as a navigator. His mother was a war widow when she met his father at the University of Wisconsin-Madison. They married and moved to Milwaukee, where Barrett was born. He grew up on the city's west side. Barrett graduated from Marquette University High School; he went on to earn his Bachelor of Arts in economics from the University of Wisconsin–Madison in 1976 and his Juris Doctor from the University of Wisconsin Law School in 1980. He helped put himself through college and law school by working on the Harley-Davidson assembly line. After law school, Barrett served as a law clerk for Judge Robert W. Warren on the United States District Court for the Eastern District of Wisconsin from 1980 to 1982. He later entered into private practice and served as a bank examiner for the Federal Deposit Insurance Corporation. State Assembly and Senate Barrett made his first run for office at the age of 28 for the Wisconsin State Assembly in 1982, but was unsuccessful. He ran again in 1984, this time successfully; he served two terms before making a successful run for the Wisconsin Senate in a December 1989 special election. He continued to serve in the Wisconsin Senate until moving to higher office in 1993. U.S. House of Representatives In 1992, after U.S. Representative Jim Moody announced his intention to run for the United States Senate, Barrett successfully ran to succeed him. Barrett was reelected four more times to represent Wisconsin's 5th congressional district,