Joseph Patrick Kennedy III (born October 4, 1980) is an American politician and diplomat who currently serves as United States Special Envoy for Northern Ireland since 2022. Prior to this, Kennedy served as the U.S. representative for Massachusetts's 4th congressional district from 2013 to 2021. A member of the Democratic Party, he represented a district that extends from Boston's western suburbs to the state's South Coast. He worked as an assistant district attorney in the Cape and Islands and Middlesex County, Massachusetts, offices before his election to Congress. In January 2021, he became a CNN commentator.

A member of the Kennedy family, he is a son of U.S. Representative Joseph P. Kennedy II, a grandson of U.S. Senator and U.S. Attorney General Robert F. Kennedy, a grandnephew of U.S. President John F. Kennedy and U.S. Senator Ted Kennedy, and a great-grandson of U.S. Ambassador to Great Britain Joseph P. Kennedy Sr.

Born in Boston, Kennedy was raised in the area with his twin brother, Matthew Rauch Kennedy. After graduating from Stanford University with a bachelor's degree, he spent two years in the Dominican Republic as a member of the Peace Corps, before earning a Juris Doctor at Harvard Law School in 2009. He resigned from his role as assistant district attorney in early 2012 to run for the U.S. House of Representatives seat held by the retiring Barney Frank. Kennedy was sworn into office in January 2013, and sat on the House Committee on Energy and Commerce.

In 2020, rather than run for re-election to his House seat, Kennedy unsuccessfully challenged incumbent Senator Ed Markey for the Democratic nomination in the Massachusetts U.S. Senate election. He was succeeded by fellow Democrat Jake Auchincloss. Since leaving office, he has founded Project Groundwork, which focuses on boosting local community organizing efforts throughout the United States. He has also joined several advisory boards and began appearing as a political commentator for CNN. On June 4, 2021, President Joe Biden appointed him to be a member of the President's Commission on White House Fellowships.

In December 2022, Kennedy was named the United States Special Envoy to Northern Ireland for Economic Affairs by President Biden.