| Mammy Johnsons River | |
| Name Other: | Mammy Johnsons Creek |
| Subdivision Type1: | Country |
| Subdivision Name1: | Australia |
| Subdivision Type2: | State |
| Subdivision Name2: | New South Wales |
| Subdivision Type3: | Region |
| Subdivision Name3: | NSW North Coast (IBRA), Mid North Coast, Upper Hunter |
| Subdivision Type5: | Local government area |
| Subdivision Name5: | Mid-Coast Council |
| Length: | 55km (34miles) |
| Source1: | Great Dividing Range |
| Source1 Location: | below Winns Mountain, northwest of Bulahdelah |
| Source1 Elevation: | 408m (1,339feet) |
| Mouth: | confluence with the Karuah River |
| Mouth Location: | north northwest of Stroud |
| Mouth Elevation: | 37m (121feet) |
| River System: | Mid-Coast Council |
| Tributaries Left: | Jeir Creek, Black Bullock Creek |
| Tributaries Right: | Wards River, Terreel Creek |
| Custom Label: | National park |
| Custom Data: | Ghin-Doo-Ee |
| Extra: | [1] |
Mammy Johnsons River, a mostly perennial river of the Mid-Coast Council[2] system, is located in the Mid North Coast and Upper Hunter regions of New South Wales, Australia.
Mammy Johnsons River rises on the southwestern slopes of the Great Dividing Range, below Winns Mountain, north northwest of Bulahdelah, and flows generally north, west and south, joined by four tributaries including Wards River, before reaching its confluence with the Karuah River north northwest of Stroud. The river descends over its course.[1]