| Mill Brook | |
| Subdivision Type1: | Country |
| Subdivision Name1: | United States |
| Subdivision Type2: | State |
| Subdivision Name2: | New York |
| Subdivision Type3: | Counties |
| Subdivision Name3: | Delaware, Ulster |
| Source1 Coordinates: | 42.0498°N -74.5907°W |
| Mouth: | Pepacton Reservoir |
| Mouth Coordinates: | 42.1162°N -74.746°W[1] |
| Mouth Elevation: | 1280feet |
Mill Brook is a river in Delaware County and Ulster County in New York. It flows into the Pepacton Reservoir west of Arena.