Edward Moore "Ted" Kennedy (February 22, 1932 – August 25, 2009) was a United States Senator from Massachusetts and a member of the Democratic Party. First elected in November 1962, he was elected nine times and served for 46 years in the U.S. Senate. At the time of his death, he was the second most senior member of the Senate, and the fourth-longest-serving senator in U.S. history. For many years the most prominent living member of the Kennedy family, he was the son of Joseph P. Kennedy, Sr., the youngest brother of President John F. Kennedy and Senator Robert F. Kennedy, both victims of assassinations, and the father of Congressman Patrick J. Kennedy.

Kennedy entered the Senate in a 1962 special election to fill the seat once held by his brother John. He was elected to a full six-year term in 1964 and was reelected seven more times. The 1969 Chappaquiddick incident resulted in the death of automobile passenger Mary Jo Kopechne; Kennedy pleaded guilty to leaving the scene of an accident, and the incident significantly damaged his chances of ever becoming President of the United States. His one attempt, in the 1980 U.S. presidential election, resulted in a primary campaign loss to incumbent Democrat Jimmy Carter.

Kennedy was known for his oratorical skills; his 1968 eulogy for his brother Robert and his 1980 Democratic National Convention rallying cry for modern American liberalism were among his best-known speeches. He became known as "The Lion of the Senate" through his long tenure and influence. More than 300 bills that Kennedy and his staff wrote were enacted into law. Unabashedly liberal, Kennedy championed an interventionist government emphasizing economic and social justice, but was also known for working with Republicans to find compromises between senators with disparate views. Kennedy played a major role in passing many laws, including laws addressing immigration, cancer research, health insurance, apartheid, disability discrimination, AIDS care, civil rights, mental health benefits, children's health insurance, education and volunteering. In the 2000s, he led several unsuccessful immigration reform efforts. Over the course of his career and continuing into the Obama administration, Kennedy continued his efforts to enact universal health care, which he called the "cause of my life."