Sunnyside is an unincorporated community in Umatilla County, Oregon, United States. It is located about three miles north of Milton-Freewater, at the intersection of Oregon Route 332, which is also known as the Sunnyside-Umapine Highway, and Oregon Route 339. Sunnyside was once a station on the Walla Walla Valley Railway, which served the local fruit orchards, and the site of a Nebraska Bridge Supply and Lumber Co.