| Loomis Brook | |
| Pushpin Map: | New York |
| Pushpin Map Caption: | Location of the mouth of Loomis Brook |
| Subdivision Type1: | Country |
| Subdivision Name1: | United States |
| Subdivision Type2: | State |
| Subdivision Name2: | New York |
| Subdivision Type4: | County |
| Subdivision Name4: | Delaware |
| Source1: | Teed Pond |
| Source1 Coordinates: | 42.2448°N -75.2079°W |
| Source1 Elevation: | NaNid = 967120 |
| Mouth: | Cannonsville Reservoir |
| Mouth Coordinates: | 42.1556°N -75.2849°W[1] |
| Mouth Elevation: | 1148feet |
| Tributaries Left: | Windfall Brook |
Loomis Brook is a river in Delaware County, New York. It flows into Cannonsville Reservoir northeast of Stilesville.