Eureka (/jɜːriːkʌ/ yer-REE-kuh) is an unincorporated community and census-designated place (CDP) in Clinton County in the U.S. state of Michigan. The community is located within Greenbush Township. As an unincorporated community, Eureka has no legal autonomy of its own but does have its own post office with the 48833 ZIP Code.