Eureka
- County:
- Humboldt County
- County Seat:
- Yes
- Area (mi²):
- 9.567
- State:
- California
Eureka is a city located in Humboldt County, California. Eureka has a 2026 population of 25,412. It is also the county seat of Humboldt County. Eureka is currently declining at a rate of -1.26% annually and its population has decreased by -4% since the most recent census, which recorded a population of 26,471 in 2020.