| Mad River | |
| Map Size: | 300 |
| Pushpin Map: | Washington#USA |
| Pushpin Map Size: | 300 |
| Pushpin Map Caption: | Location of the mouth of the Mad River in Washington |
| Subdivision Type1: | Country |
| Subdivision Name1: | United States |
| Subdivision Type2: | State |
| Subdivision Name2: | Washington |
| Subdivision Type4: | County |
| Subdivision Name4: | Chelan |
| Discharge1 Location: | river mile 0.4 at Ardenvoir[1] |
| Discharge1 Min: | 9cuft/s |
| Discharge1 Avg: | 76.7cuft/s[2] |
| Discharge1 Max: | 659cuft/s |
| Source1: | Cascade Range |
| Source1 Coordinates: | 47.9417°N -120.6478°W |
| Mouth: | Entiat River |
| Mouth Coordinates: | 47.7358°N -120.3633°W |
| Basin Size: | 92.4sqmi |
The Mad River is a river in the U.S. state of Washington. It rises in the Cascade Mountains and flows southeast to join the Entiat River. It is part of the Columbia River basin, being a tributary of the Entiat River, which empties into the Columbia River.