David T. Prosser Jr. (born December 24, 1942) is an American jurist and politician who served as Speaker of the Wisconsin State Assembly from 1995 to 1996, and as a justice of the Wisconsin Supreme Court from 1998 to 2016.

Following his graduation from University of Wisconsin Law School, Prosser worked in Washington as an attorney at the U.S. Department of Justice and as an aide to U. S. Representative Harold Vernon Froehlich. Returning to Wisconsin, he began a private practice, worked as a district attorney for two years, then served 18 years as a Republican party legislator in the Wisconsin State Assembly. He was the state house minority leader for six of those years and Speaker of the Assembly for two years.

After an unsuccessful bid for the U.S. House in 1996, Prosser was appointed by Wisconsin Governor Tommy Thompson to a vacant seat on the state tax appeals board, then in 1998 to a vacant seat on Wisconsin Supreme Court. He was elected to his first 10-year term without opposition in 2001. He ran for reelection in April 2011 against little-known Wisconsin assistant attorney general JoAnne Kloppenburg. The race received national attention and was viewed as a referendum on efforts by Republican Governor Scott Walker and the Republican-controlled legislature to curb the union rights of public workers in Wisconsin. The April 5, 2011 election was too close to call until two days later when the Waukesha County Clerk announced she had erroneously omitted more than 14,000 votes from her earlier tally. The additional votes gave Prosser a lead of over 7,000 which was sustained by a later recount.

Prosser received media attention in 2010 following verbal altercations with the chief justice of the Wisconsin Supreme Court, and also in June 2011 when allegations were made of a physical altercation between Prosser and fellow associate justice Ann Walsh Bradley that occurred in connection with the union-curbing bill. A special prosecutor investigated but declined to press criminal charges. An ethics action against Prosser was recommended by the Wisconsin Judicial Commission, however, after three other justices recused themselves from the matter, no further action was taken.