Cosna Slough is a stream located in Yukon-Koyukuk County, Alaska. It appears on the Kantishna River D-3 NW USGS 7.5-minute topographic quadrangle. The elevation at this location is approximately 235.04 feet (71.64 m) above sea level. The nearest populated place is Cos Jacket, approximately 1.2 miles to the S.