The Prospect Hill Historic District encompasses a large residential area in the Willimantic section of Windham, Connecticut.

It is roughly bounded by Valley, Jackson, Bolivia, Washburn, Windham, and High Streets, and contains one of the state's largest single concentrations of Victorian-era residential architecture.

In the first half of the 19th century, the mill privileges were converted to textile manufacturing, and were greatly expanded.

The city also benefited from the convergence of several railroad lines, making it an important regional transit center.

Dominant architectural styles are those that predate the First World War: Italianate, Second Empire, Queen Anne Victorian, Stick and Shingle styles are all well represented, although a substantial number of the examples are in vernacular forms.