| Official Name: | Assu |
| Settlement Type: | Municipality |
| Pushpin Map: | Brazil |
| Pushpin Map Caption: | Location in Brazil |
| Coordinates: | -5.5769°N -36.9089°W |
| Subdivision Type: | Country |
| Subdivision Name: | Brazil |
| Subdivision Type1: | Region |
| Subdivision Name1: | Northeast |
| Subdivision Type2: | State |
| Subdivision Name2: | Rio Grande do Norte |
| Subdivision Type3: | Mesoregion |
| Subdivision Type4: | Microregion |
| Subdivision Type5: | Metrop. region |
| Leader Title: | Mayor |
| Area Total Km2: | 1303 |
| Population Total: | 58,384 |
| Population As Of: | 2020 [1] |
| Population Density Km2: | auto |
| Timezone1: | BRT |
| Utc Offset1: | -03:00 |
| Postal Code Type: | Postal code |
| Area Code Type: | Area code |
Açu (or Assu) is a municipality (município) in the state of Rio Grande do Norte in Brazil. The population is 58,384 (2020 est.) in an area of 1303 km².[2]
The municipality contains the Açu National Forest, a sustainable use conservation unit that was originally established as a forest park in 1950.The Barragem Armando Ribeiro Gonçalves, a reservoir on the Piranhas River, is partly located in the municipality.