Yolo County is located in the northern part of the U.S. state of California, bordered by the counties of Sacramento, Solano, Napa, Lake, Colusa, and Sutter. Woodland is the county seat.

As of the 2000 census, Yolo County had a population of 168,660, and notwithstanding the presence of the University of California, Davis in its midst and the state capital in the neighboring county of Sacramento, Yolo County remains a relatively rural agricultural area, home to the multi-billion dollar California tomato industry, which dominates 90% of the tomato market in the United States.

Yolo County is part of the Sacramento-Arden-Arcade-Roseville Metropolitan Statistical Area.