Scappoose Bay is a slough of Multnomah Channel, a distributary of the Willamette River, about 1 mile (1.6 km) upstream of where the channel meets the Columbia River in Columbia County, Oregon, United States.

It is surrounded by a broad wetland area full of small ponds and other waterways across from Sauvie Island.

[3] Lying in the upper portion of the Columbia River Estuary, Scappoose Bay is tidal but is a freshwater body.

During the 19th century, American settlers developed the area, clearing land for farming.

[6][7] An advisory from the Oregon Department of Environmental Quality against consuming fish and shellfish from the bay remains in effect due to contamination from former industrial activity.