Arlen Specter (February 12, 1930 – October 14, 2012) was an American lawyer, author and politician who served as a United States Senator from Pennsylvania from 1981 to 2011. Specter was a Democrat from 1951 to 1965, then a Republican from 1965 until 2009, when he switched back to the Democratic Party. First elected in 1980, he was the longest-serving senator from Pennsylvania, having represented the state for 30 years.

Specter was born in Wichita, Kansas, to immigrant Russian/Ukrainian Jewish parents. He graduated from the University of Pennsylvania and served with the United States Air Force during the Korean War. Specter later graduated from Yale Law School and opened a law firm with Marvin Katz, who would later become a federal judge. Specter served as assistant counsel for the Warren Commission investigating the assassination of John F. Kennedy and helped formulate the "single-bullet theory". In 1965, Specter was elected District Attorney of Philadelphia, a position that he held until 1973.

During his 30-year Senate career, Specter staked out a spot in the political center. He served as Chair of the Senate Judiciary Committee from 2005 to 2007. In 2006, Specter was selected by Time as one of America's Ten Best Senators. Specter lost his 2010 re-election bid in the Democratic primary to former U.S. Navy vice admiral Joe Sestak, who then lost to Republican Pat Toomey in the general election. Toomey succeeded Specter on January 3, 2011.

In 1993, Specter underwent a surgery to remove a brain tumor. In early 2005 he was diagnosed with Hodgkin's lymphoma, but continued his work in the Senate while undergoing chemotherapy. He died from complications of non-Hodgkin's lymphoma on October 14, 2012.