Agriculture is a significant sector in California's economy, producing nearly US$50 billion in revenue in 2018. There are more than 400 commodity crops grown across California, including a significant portion of all fruits, vegetables, and nuts in the United States. In 2017, there were 77,100 unique farms and ranches in the state, operating across 25.3 million acres of land. The average farm size was 328 acres (133 ha), significantly less than the average farm size in the U.S. of 444 acres (180 ha).

The economy of the State of California is the largest in the United States, with a $3.89 trillion gross state product (GSP) as of 2023. It is the largest sub-national economy in the world. If California were a sovereign nation (2024), it would rank in terms of nominal GDP as the world's Sixth largest economy, ahead of the United Kingdom. California Poised to Become World's 6th Biggest Economy Additionally, California's Silicon Valley is home to some of the world's most valuable technology companies, including Apple, Alphabet, and Nvidia. In total, 11 of the Fortune 100 companies and 53 of the Fortune 500 companies are headquartered in California.