The 25th Senate District of Wisconsin is one of 33 districts in the Wisconsin Senate. Located in northwest Wisconsin, where Wisconsin meets Lake Superior, the district comprises all of Ashland, Bayfield, Burnett, Douglas, Iron, Polk, Sawyer, and Washburn counties. It contains the cities of Superior, Ashland, Bayfield, Hayward, Spooner, and Washburn. The district also includes the Bad River Indian reservation and the Chequamegon–Nicolet National Forest.

The Wisconsin Senate is the upper house of the Wisconsin State Legislature. Together with the larger Wisconsin State Assembly they constitute the legislative branch of the state of Wisconsin. The powers of the Wisconsin Senate are modeled after those of the U.S. Senate.