William Orville Douglas (October 16, 1898 – January 19, 1980) was an American jurist who served as an associate justice of the Supreme Court of the United States from 1939 to 1975. Douglas was known for his strong progressive and civil libertarian views and is often cited as the most liberal justice in the U.S. Supreme Court’s history. Nominated by President Franklin D. Roosevelt in 1939, Douglas was confirmed at the age of 40, becoming one of the youngest justices appointed to the court. He is the longest-serving justice in history, having served for 36 years and 209 days.