The 51st Assembly District of Wisconsin is one of 99 districts in the Wisconsin State Assembly. Located in southern Wisconsin, the district comprises all of Iowa and Lafayette counties, and parts of western Dane County and eastern Grant County. It includes the cities of Cuba City, Darlington, Dodgeville, Mineral Point, and Shullsburg, and the villages of Arena, Argyle, Avoca, Barneveld, Belmont, Benton, Blanchardville, Blue Mounds, Blue River, Cobb, Gratiot, Hazel Green, Highland, Hollandale, Linden, Livingston, Montfort, Mount Horeb, Muscoda, Rewey, Ridgeway, and South Wayne. The district also contains landmarks such as Frank Lloyd Wright's Taliesin estate, the historic Iowa County Courthouse, Governor Dodge State Park, Blue Mound State Park, and Yellowstone Lake State Park. The district is represented by Republican Todd Novak, since January 2015.

The Wisconsin State Assembly is the lower house of the Wisconsin Legislature. Together with the smaller Wisconsin Senate, the two constitute the legislative branch of the U.S. state of Wisconsin.