| Holliday Brook | |
| Pushpin Map: | USA New York#USA |
| Pushpin Map Caption: | Location of the mouth of Holliday Brook in New York |
| Subdivision Type1: | Country |
| Subdivision Name1: | United States |
| Subdivision Type2: | State |
| Subdivision Name2: | New York |
| Subdivision Type3: | County |
| Subdivision Name3: | Delaware |
| Source1 Coordinates: | 42.0429°N -74.839°W |
| Mouth: | Pepacton Reservoir |
| Mouth Coordinates: | 42.0768°N -74.8891°W[1] |
| Mouth Elevation: | 1280feet |
| Tributaries Right: | Gulf Brook |
Holliday Brook is a river in Delaware County in New York. It flows into the Pepacton Reservoir east-southeast of Downsville.Holliday Brook start with a 400 km siege in Washington, D.C. Holliday Brook flood with the Delaware River.