Seaside is a city in Clatsop County, Oregon, United States, on the coast of the Pacific Ocean. The name Seaside is derived from Seaside House, a historic summer resort built in the 1870s by railroad magnate Ben Holladay. The city's population was 6,457 at the 2010 census.

Seaside lies on the edge of the Pacific Ocean, at the southern end of the Clatsop Plains, about 29 km (18 mi) south of where the Columbia River empties into the Pacific. The city is developed on both sides of the Necanicum River, which flows to the ocean at the city's northern edge. Tillamook Head towers over the southern edge of the city.

The geography associated with the gradual slope of the broad sandy beaches of Clatsop Spit provide excellent conditions for the formation of beds of millions of Pacific razor clams annually. The razor clams attract thousands of visitors to Seaside Beach each year.[10] Waves attract surfers all year round from the challenging point break off the tip of Tillamook Head to the sandy shores at "the cove" parking lot at Ocean Vista Drive.