Blow-me-down Brook is a 12.8-mile (20.6 km) long[1] stream located in western New Hampshire in the United States.

Blow-me-down Brook begins near the northeast border of the town of Cornish, New Hampshire, below Stowell Hill.

It flows west, passing through the village of Cornish Flat, where it is joined by Notch Brook, then flows northwest into the town of Plainfield, where it takes a zig-zag course generally west, reentering Cornish shortly before its end at the Connecticut River.

In its lower course in Cornish, the brook passes the village of Squag City and Saint-Gaudens National Historic Site.

The brook was dredged from a small dam at the northeastern edge of Cornish Flat to the bridge that crosses State Route 120.