Knappa is an unincorporated community located on the south bank of the Columbia River in Clatsop County, Oregon, United States, approximately 12 miles (19 km) directly east of Astoria. Knappa faces the Columbia River, where several islands comprise the Lewis and Clark National Wildlife Refuge.
The community is named after Aaron Knapp, Jr., an early settler. There was a post office in Knappa from 1872 to 1943. It is vulnerable to a Cascadia Subduction Zone tsunami.
Logging and fishing are the primary economic activities in Knappa.Knappa School District comprises Hilda Lahti Elementary School and Knappa High School.