The 3rd Senate District of Wisconsin is one of 33 districts in the Wisconsin Senate. Located in southeast Wisconsin, the district is entirely contained within central Milwaukee County. It comprises much of the south side of the city of Milwaukee, as well as the village of West Milwaukee and eastern parts of the cities of West Allis and Greenfield. The district contains landmarks such as American Family Field, Walker's Point Historic District, the Mitchell Park Domes, and the historic Forest Home Cemetery. The district also contains the largest concentration of Hispanic residents in Wisconsin, at 45% of the district population.

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.