The descriptive physical oceanography of the California Current System has been well reviewed in the literature. In this chapter I provide an up to date summary of the features that are most relevant to fisheries oceanography. I start with the various regional physical classifications of the California Current System, followed by the main bathymetric features of the core CalCOFI area. I describe the water sources and properties, and then the geostrophically mapped currents. The relative importance of advection and upwelling to production in the California Current System is a key theme of this chapter. I describe the seasonal cycle based on remote sensing, and the spring transition from winter to upwelling conditions. I address processes affecting biological production off central California, and both in and offshore of the Southern California Bight (SCB). These processes include advection, geostrophic adjustment, wind stress curl, seasonal overturn, Sverdrup transport, wind-driven upwelling and wind relaxation events. I discuss important processes and structures in their regional context. Wind-driven coastal upwelling, wind-relaxation events, and eddy-like flows are more important off central California. Geostrophic adjustment, seasonal convective overturn, wind stress curl, Sverdrup transport in the nearshore, the deep chlorophyll maximum and fronts are described in the context of southern California.