Thomas Dale DeLay (/dəˈleɪ/; born April 8, 1947) is an American author and retired politician who served as a member of the United States House of Representatives. A Republican, DeLay represented Texas's 22nd congressional district from 1985 until 2006. He served as House majority leader from 2003 to 2005.

DeLay began his political career in 1978 when he was elected to the Texas House of Representatives. He was first elected to the U.S. House of Representatives in 1984. In 1988, DeLay was appointed deputy minority whip. In 1994, he helped Newt Gingrich orchestrate the Republican Revolution, which swept Democrats from power in both houses of Congress and put Republicans in control of the House of Representatives for the first time in forty years. In 1995, DeLay was elected House majority whip. With the Republicans in control of both chambers in Congress, DeLay and conservative activist Grover Norquist helped start the K Street Project in an effort to advance Republican ideals. DeLay was elected House majority leader after the 2002 midterm elections. He was known as a staunch conservative during his years in Congress.

In 2005, a Travis County grand jury indicted DeLay on criminal charges of conspiracy to violate election law by campaign money laundering. DeLay temporarily resigned from his position as House majority leader and later announced that he would not seek to return. He resigned his seat in Congress in June 2006. DeLay was convicted in January 2011 and sentenced to three years in prison, but was free on bail while appealing his conviction. The trial court's judgment was overturned by the Austin Court of Appeals, a Texas intermediate appellate court, on September 19, 2013; the Court of Appeals ruled that "the evidence in the case was 'legally insufficient to sustain DeLay's convictions'", and acquitted DeLay. The acquittal was upheld on appeal.

After leaving Congress, DeLay co-authored a political memoir entitled No Retreat, No Surrender: One American's Fight. He also founded First Principles, LLC, a lobbying firm.

DeLay was born in Laredo, Texas, one of three sons of Maxine Evelyn (née Wimbish) and Charles Ray DeLay. He spent most of his childhood in Venezuela due to his father's work in the petroleum and natural gas industry. He attended Calallen High School in Corpus Christi, Texas, where he both played football and was the lead dancer in school productions. He attended Baylor University for two years, majoring in pre-med, but was expelled for drinking and painting Baylor school colors on a building at rival Texas A&M University. The Washington Post reported that DeLay "received student draft deferments during the Vietnam era and avoided military service through the 1969 lottery". At the 1988 Republican Convention, he said that he could not volunteer to fight in Vietnam because so many minority youths had volunteered that there was literally no room for "patriotic folks" like himself.

DeLay graduated from the University of Houston in 1970 with a Bachelor of Science in biology.

After graduating from college, DeLay spent three years at pesticide-maker Redwood Chemical and then purchased Albo Pest Control, which DeLay grew into a large and successful business. This work was the source for his nickname, "the Exterminator". In the 11 years DeLay ran the company, the Internal Revenue Service imposed three tax liens on him for failure to pay payroll and income taxes. The United States Environmental Protection Agency's ban on Mirex, a pesticide that was used in extermination work, led DeLay to oppose government regulation of businesses, a belief that he has carried with him throughout his political career.

In 1978, DeLay won the election for an open seat in the Texas House of Representatives. He was the first Republican to represent Fort Bend County in the state House. He was first sworn in on January 9, 1979, as a representative from the 21st district and served in the state House until 1985. DeLay ran for U.S. Congress in 1984 from the 22nd District, after fellow Republican Ron Paul decided to run in the Republican primary for the 1984 U.S. Senate race instead of for reelection (Paul subsequently returned to Congress from a neighboring district). He easily won a crowded six-way primary with 53 percent of the vote, and cruised to election in November. DeLay was one of six freshmen Republican congressmen elected from Texas in 1984 known as the Texas Six Pack. He was reelected 10 times, never facing substantive opposition in what had become a solidly Republican district.^{[citation needed]}