| Settlement Type: | municipality |
| Official Name: | Alto Parnaíba |
| Subdivision Type: | Country |
| Subdivision Type1: | Region |
| Subdivision Type2: | State |
| Subdivision Name: | Brazil |
| Subdivision Name1: | Northeast |
| Subdivision Name2: | Maranhão |
| Leader Title: | Mayor |
| Leader Name: | Ranieri Avelino Soares |
| Established Title: | Founded |
| Established Date: | May 19, 1866 |
| Area Total Km2: | 11132.105 |
| Population As Of: | 2020 [1] |
| Population Total: | 11,212 |
| Population Density Km2: | 0.9 |
| Timezone: | BRT |
| Utc Offset: | -3 |
| Coordinates: | -9.1108°N -45.93°W |
| Blank Name: | HDI (2000) |
| Blank Info: | 0.636 – medium[2] |
Alto Parnaíba is a Brazilian municipality in the southernmost tip of the state of Maranhão. In 2020, the city's population was 11,212.
The municipality contains part of the Nascentes do Rio Parnaíba National Park, created in 2002.
Alto Parnaíba experiences a tropical savanna climate (Köppen: Aw) with hot temperatures and distinct wet and dry seasons.
The city experiences a wet season from November to April. The dry season extends from May to September, with June through August having almost no rainfall.
Alto Parnaíba has hot and humid conditions throughout the year. September and October, before the wet season, are the hottest months, with average highs around 36C.