California's 1st state senatorial district is one of 40 California State Senate districts.

The district is represented by Republican Megan Dahle of Bieber.

The district includes most of the California Cascades, northern Sierra Nevada and the Sacramento Valley, comprising Siskiyou, Modoc, Lassen, Shasta, Tehama, Plumas, Glenn, Colusa, Butte, Sutter, Yuba, Nevada, and Sierra Counties, along with eastern Placer County.