Alvada /ælˈveɪdə/ is an unincorporated community in western Big Spring Township, Seneca County, Ohio, United States. Although it is unincorporated, it has a post office, with the ZIP code of 44802. It is located along the concurrency of U.S. Route 23 and State Route 199.A post office called Alvada has been in operation since 1877. By 1880, Alvada had 63 inhabitants.