The Harrison River is a short but large tributary of the Fraser River, entering it near the community of Chehalis, British Columbia. The Harrison drains Harrison Lake and is the de facto continuation of the Lillooet River, which feeds the lake.
The Harrison is navigable, although in the days of the Fraser Canyon Gold Rush of it was necessary to dredge the sandbars at the confluence with the Fraser, which were known as "the Riffles". There are also small rapids and difficult water in the first stretch of the river downstream from Harrison Lake, which is a forested canyon.
Below the confluence of the Chehalis River, at the bridge between Chehalis and the Municipality of Kent, the river widens into a wide backwater, Harrison Bay, then from there joins the Fraser. In addition to the aforementioned bridge (Hwy 7) the Harrison is also crossed by the mainline of the Canadian Pacific Railway.