Voters in the 20 odd-numbered districts of the California State Senate elected their representatives.

[4] The 3rd district encompasses the northern San Francisco Bay Area and the Sacramento–San Joaquin River Delta regions.

It includes parts of the North Bay, Wine Country, and the Sacramento Valley.

[8] The 13th district encompasses the San Francisco Peninsula and the northwestern reaches of Silicon Valley.

[8] The 23rd district encompasses a wide arc of the Inland Empire, circling clockwise from Rancho Cucamonga in the northwest to Menifee in the south.

It also includes several resort communities in the San Bernardino Mountains and a sliver of the High Desert.

It encompasses the northern Santa Ana Valley, including western and central Anaheim, Fullerton, and Yorba Linda.

[8] The 37th district encompasses central Orange County, centered on eastern Anaheim and Irvine.

The incumbent is Democrat State Senate President pro tempore Toni Atkins, who was elected with 62.5% of the vote in 2016.