Patrick Joseph Leahy OBE (born March 31, 1940) is an American politician and attorney who represented Vermont in the United States Senate from 1975 to 2023. A member of the Democratic Party, he also was the president pro tempore of the United States Senate from 2012 to 2015 and from 2021 to 2023.

Leahy was the third-longest-serving U.S. senator in history at 48 years, and was the longest-serving member of the United States Congress to serve solely as a senator.