Ashfield lies in the eastern foothills of The Berkshires, with several high hills, including Ridge Hill, in the northern portion of town. The town is fed by several rivers and brooks, including the South River, the "western" Swift River (the "eastern" river flows out of the Quabbin Reservoir in central Massachusetts) and several prominent brooks, most of which feed into either the Deerfield River or the Connecticut River. Near the center of town, Ashfield Lake feeds into the South River, and is a recreational site. In the southwest portion of town, a small portion of the Poland Brook Wildlife Management Area crosses into town, as does a portion of the Daughters of the American Revolution State Forest.