The Western theater of the American Revolutionary War involved military campaigns in regions that are today part of the Midwestern United States, mainly focusing on the Ohio Country, Illinois Country, and parts of present-day Indiana and Kentucky. The theater was characterized by sporadic fighting and skirmishes between British forces, along with their Native American allies, and American settlers and militia. Notable figures in this theater included American General George Rogers Clark, who led a small force that captured British posts in the Illinois Country, effectively securing territory in the Midwest for the American cause.

One of the most significant campaigns in the Western theater was Clark's 1778-1779 Illinois Campaign. Clark captured Kaskaskia and Cahokia without firing a shot, mainly due to the element of surprise. He then moved against Vincennes, capturing it and taking the British Lt. Governor Henry Hamilton prisoner. The capture of these forts weakened British influence in the region and garnered French and Native American support for the American cause. This helped to secure the western frontier and kept British and Native American forces occupied, preventing them from reinforcing British troops in the eastern theater.

The Western theater was vital for both sides in terms of strategic resources and support from Native American tribes. British forts such as Detroit served as important staging points for raids into American territory. Native American alliances were actively sought by both sides, but despite some successes for the British and their Native American allies in the form of raids and skirmishes, the American capture and control of key posts weakened British influence and contributed to American victory. The actions in the Western theater, though less renowned than those in the East, played a significant role in stretching British resources thin and adding to the geopolitical complexity that ultimately favored the American cause.