Silicon Valley is the southern part of the San Francisco Bay Area in Northern California in the United States. The term originally referred to the region's large number of silicon chip innovators and manufacturers, but eventually came to refer to all the high-tech businesses in the area; it is now generally used as a metonym for the high-tech sector. Despite the development of other high-tech economic centers throughout the United States, Silicon Valley continues to be the leading high-tech hub because of its large number of engineers and venture capitalists.

Geographically, "Silicon Valley" encompasses the northern part of Santa Clara Valley and adjacent communities in the southern parts of the San Francisco Peninsula and East Bay. It now reaches approximately from San Mateo (on the Peninsula) and the Fremont/Newark area in the East Bay down through San Jose, centered roughly on Sunnyvale. The Highway 17 corridor through the Santa Cruz Mountains into Scotts Valley and Santa Cruz in Santa Cruz County is sometimes considered a part of Silicon Valley.