Thomas M. Nelson (born March 3, 1976) is an American public administrator and politician serving as the county executive of Outagamie County, Wisconsin since 2011. A member of the Democratic Party, Nelson previously served in the Wisconsin State Assembly for six years, and was the Democratic majority leader for the 2009–2010 session. He was a candidate in the 2022 Democratic primary election for the United States Senate, he withdrew from the race in late July and endorsed Mandela Barnes.