William Johnson Jr. (December 27, 1771 – August 4, 1834) was an American attorney, state legislator, and jurist who served as an Associate Justice of the Supreme Court of the United States from 1804 to 1834. When he was 32 years old, Johnson was appointed to the Supreme Court by President Thomas Jefferson. He was the first Jeffersonian Republican member of the Court as well as the second Justice from the state of South Carolina. During his tenure, Johnson restored the act of delivering seriatim opinions. He wrote about half of the dissents during the Marshall Court, leading historians to nickname him the "first dissenter".