Patrick Joseph Leahy (pronounced /leihi/; born March 31, 1940) is the senior United States Senator from Vermont and member of the Democratic Party. He is the first and only elected Democratic United States Senator in Vermont's history. He is the chairman of the Senate Judiciary Committee. Leahy is the second most senior U.S. Senator, and second longest-serving Democrat in the U.S. Senate having served since 1975.

On September 20, 2010, Leahy introduced the Combating Online Infringement and Counterfeits Act, Senate Bill S.3804, which would allow the court to issue a restraining order or injunction against Internet domain names which infringe upon copyright. After this bill failed to get approved, Leahy introduced the Protect IP Act (PIPA) to the Senate on May 12, 2011, - the act was drafted to support the entertainment industry by preventing illegal copying of music and movies on the internet especially abroad, but critics maintain that it would be ineffective, impede free expression the internet, and interfere with its infrastructure. Leahy subsequently indicated that he would favor further research into provisions that raised objections.