MacMillan Provincial Park is a 301 hectare provincial park in British Columbia, Canada. Located 25 km west of Qualicum Beach and 16 km east of Port Alberni, the park straddles Highway 4 in central Vancouver Island. It is nestled on the western shore of Cameron Lake, and protects the delta of the Cameron River. The park is home to a famous, 157 hectare stand of ancient Douglas-fir, known as Cathedral Grove, which draws visitors from all over the world. The park provides the only highway-accessible protected old-growth Douglas-fir forest in British Columbia.