Colonial Glacier is in North Cascades National Park in the U.S. state of Washington and is immediately northwest of Neve Peak. Colonial Glacier flows generally north, descending from . Between 1950 and 2006, Colonial Glacier is estimated to have retreated more than and a newly formed proglacial lake filled the recently vacated former terminal moraine. The reduction in size of the glaciers of the North Cascades will reduce summertime meltwater runoff which is used to maintain a steady supply of electricity from hydroelectric power plants.