| Official Name: | Municipality of Pio IX |
| Native Name: | Município de Pio IX |
| Subdivision Type: | Country |
| Subdivision Name: | Brazil |
| Subdivision Type1: | Region |
| Subdivision Name1: | Northeast |
| Subdivision Type2: | State |
| Subdivision Name2: | Piauí |
| Leader Title: | Mayor |
| Leader Name: | Jose Mesquita Viana de Andrade (PSDB) |
| Established Title: | Settled |
| Established Date: | January 1, 1939 |
| Area Total Km2: | 1948.843 |
| Population As Of: | 2020 [1] |
| Population Total: | 18,459 |
| Population Density Km2: | 8.6 |
| Timezone: | BRT |
| Utc Offset: | -3 |
| Coordinates: | -6.8378°N -40.5789°W |
| Elevation M: | 495 |
| Blank Name: | HDI (2000) |
| Blank Info: | 0.572 – medium[2] |
Pio IX is the easternmost city in the Brazilian state of Piauí. The city is named after Pope Pius IX.