Alexander Stewart Provincial Park is a nature reserve in McNab/Braeside, Renfrew County, Ontario, Canada, about 11 kilometres (7 mi) west of the centre of Arnprior. This nature reserve contains a hardwood forest of several species including maple, American beech, basswood, blue-beech, and bur oak. The subsurface is clay silt, a remnant of the ice age Champlain Sea. The site is at an elevation of 130 metres (430 ft). The property was bought in 1860 by the eponymous Alexander Stewart, and donated by his children to the province in 1966.