Forbidden Glacier lies on the north slopes of Forbidden Peak in Washington's North Cascades National Park, high in the rugged center of the range. Its meltwater flows into Moraine Lake. The glacier is about 0.75 miles long and roughly 1 mile wide at its terminus, dropping from around 8,000 feet to about 5,600 feet in elevation. An arête divides it from Boston Glacier to the east and south, highlighting the steep, sharply sculpted terrain surrounding Forbidden Peak.