California's 3rd senatorial district is one of 40 California State Senate districts. It is currently represented by of .
Spanning 3,000 square miles, the district includes California Wine Country, the Sacramento-San Joaquin River Delta, and University of California, Davis, and consists of Napa, Yolo, and Solano Counties as well as parts of Sonoma, Contra Costa, and Sacramento Counties.
Due to redistricting, the 3rd district has been moved around different parts of the state. The current iteration resulted from the 2021 redistricting by the California Citizens Redistricting Commission.