Allendale is a census-designated place (CDP) in Solano County, California, United States.

Allendale is located along Interstate 505 6.5 miles (10.5 km) west of Dixon.

According to the United States Census Bureau, the CDP covers an area of 6.2 square miles (16.1 km2), 98.98% of it land and 1.02% of it water.

The 2010 United States Census[19] reported that 1,506 people, 528 households, and 431 families resided in the CDP.

Allendale, CA, is the setting of Ray Bradbury's short story, "There Will Come Soft Rains".