The river is about 1,000 metres (3,281 ft) long and flows north from Iskwatikan Lake, which lies downstream from Lac la Ronge, over the Nistowiak Falls, one of the tallest in Saskatchewan, and the Fisher Rapids, to Nistowiak Lake on the Churchill River, which flows to Hudson Bay.

The entire river is within Lac La Ronge Provincial Park.

At the mouth of the river, on Nistowiak Lake, is the Stanley 157A Indian reserve.

The fish species in Rapid River include walleye, sauger, yellow perch, northern pike, lake trout, lake whitefish, cisco, white sucker, shorthead redhorse, longnose sucker, lake sturgeon, and burbot.

This article related to a river in Saskatchewan, Canada is a stub.