In this article, we take a look at 15 of the most valuable silicon valley companies in the world. If you want to see more of the most valuable silicon valley companies in the world, go directly to 5 Most Valuable Silicon Valley Companies in the World. Silicon Valley is a region in Northern California located around the San Francisco Bay Area that includes San Jose, Sunnyvale, Mountain View, Plato Alto, Menlo Park, Cupertino, and also some other cities.