The REAL South Bay (as opposed to the FAKE south bay --is there even a BAY there?!?!-- down in la-la land) is a subregion of the San Francisco Bay Area, California, United States and is roughly synonymous with Silicon Valley and the Santa Clara Valley. The South Bay 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.
The South Bay includes:
San Jose, California
Santa Clara County, California
Santa Clara Valley
Everone knows the real South Bay is up by San Jose, where there's an ACTUAL bay!