The North Santiam River is a tributary of the Santiam River, approximately 90 mi (145 km) long, in western Oregon in the United States. It drains an area of the Cascade Range on the western side of the Willamette Valley east of Salem.

It rises in the high Cascades in eastern Linn county, northwest of Three Fingered Jack in the Willamette National Forest. It flows north through the mountains past Marion Forks , receiving the drainage from the westerns slope of Mt. Jefferson. Near Mt. Jefferson it turns sharply west, descending through a canyon past Idanha, Detroit, and Gates. It emerges through the foothills into the Willamette Valley near Stayton, then flows briefly southwest through the valley where it joins the South Santiam River from the northeast to form the Santiam approximately 15 mi (24 km) southwest of Stayton. The confluence is approximately 10 mi (16 km) east of the confluence of the Santiam and the Willamette River.

It is impounded by Detroit Dam in the mountains west of Detroit to form Detroit Lake for flood control. Detroit Lake State Park is located along the southern shore of the lake.

In the 19th century the canyon of the North Santiam River provided a formidable obstacle to settlers. The construction of a railroad in 1887 opened up the canyon to settlement and logging of the surrounding mountains.