The Santa Clara Valley is a valley just south of the San Francisco Bay in northern California in the United States. Much of Santa Clara County, California is in the Santa Clara Valley. The valley was originally known as the Valley of Heart's Delight for the miles and miles of fruit trees blossoming in the spring. Once primarily agricultural because of its highly fertile soil, it is now largely urbanized. Silicon Valley is roughly synonymous with the Santa Clara Valley, although since the former is as much a state of mind as an actual location, people often refer to parts of the San Francisco Peninsula as being part of Silicon Valley as well. Locally, the Santa Clara Valley is also referred to as the "South Bay."

The northern end of the Santa Clara Valley is at the southern tip of the San Francisco Bay, and the southern end is in the vicinity of Gilroy. The valley is bounded by the Santa Cruz Mountains on the southwest and by the Diablo Range on the northeast. It is about 30 miles long and about 15 miles wide. The valley's largest city, by far, is San Jose.

Cities and towns in the Santa Clara Valley include (in alphabetical order):

• Campbell
• Cupertino
• Gilroy
• Los Altos
• Los Altos Hills
• Los Gatos
• Milpitas
• Morgan Hill
• Mountain View
• San Jose
• San Martin
• Santa Clara
• Saratoga
• Sunnyvale

Because so much high-tech industry has spread out from the valley, Fremont and Newark, even though they are not in the Santa Clara Valley, are often included in discussions about Silicon Valley or, in the case of Fremont, is referred to as the Gateway to Silicon Valley (a title also claimed occasionally by San Jose). Similarly, Palo Alto, while in Santa Clara County and considered part of Silicon Valley, is on the San Francisco Peninsula.