santa clara county, officially the county of santa clara, is a county in the san francisco bay area in state of california, united states. as of the 2010 census, the population was 1,781,642. it is sixth largest county in the state of california by population. the county seat and largest city is san jose. santa clara county's population in 2017 is estimated to be larger than the population of fourteen u.s. states and of the district of coumbia.