Joseph A. "Joe" Sestak, Jr. (born December 12, 1951) is a retired United States Navy Rear Admiral and currently a Democratic member of the United States House of Representatives, representing Pennsylvania's 7th congressional district (map) since 2007. The district incorporates parts of the Philadelphia suburbs, including most of Delaware County.

Sestak is the highest-ranking former military officer currently serving in this Congress. His legislative efforts have resulted in House Majority Leader Steny Hoyer naming him the most productive freshman member of Congress in 2007. On August 4, 2009, Sestak declared his candidacy for the U.S. Senate, posing a primary challenge against Senator Arlen Specter.

Sestak was born in Secane, Pennsylvania. He graduated from Cardinal O'Hara High School in Springfield, a suburb of Philadelphia in Delaware County. His grandfather, Martin, came to America from the village of Dolné Lovčice in Slovakia in 1922, after World War I, while his father Joseph (age 3), was sent to America in 1924 to join Martin. Sestak's father graduated from the U.S. Naval Academy in 1942, and then fought in both the Atlantic and the Pacific during World War II. Following in his father's footsteps, Sestak graduated from the U.S. Naval Academy in 1974 with a Bachelor of Science degree in American political systems. Between tours at sea, Sestak earned a Master of Public Administration and a Ph.D. in political economy and government from the John F. Kennedy School of Government at Harvard University in 1980 and 1984, respectively.