Old Town Eureka (formally the Eureka Old Town Historic District) in Eureka, California, is a historic district listed on the United States National Register of Historic Places.

The core of the district runs the length of First, Second, and Third Streets, between "C" and "M" Streets, and includes many types of architecture including Eastlake, Queen Ann, Greek Revival, Classical Revival, and Second Empire styles from the 1850s to the 20th century.

The city began as an 1850 settlement on the edge of Humboldt Bay.

Developers and settlers planned for Eureka to aid in the provision of miners working inland to the east.

By 1865, the central core of what would become Eureka's "Old Town" was considered "a lively place for a small town, full of business and with plenty of money."