Decius Spear Wade (January 23, 1835 – August 3, 1905) was an American attorney, judge, writer, and politician who has been called the "Father of Montana Jurisprudence" for his role in establishing the common law and statutory law of the U.S. state of Montana. He was a judge and state senator in Ohio before serving sixteen years as Chief Justice of the Montana Territorial Supreme Court. As a member of the post-statehood Code Commission, he was one of the main drafters of the and the most vocal advocate in the state for codification.