| São Sebastião | |
| Settlement Type: | Municipality of Alagoas, Brazil |
| Flag Alt: | Flag of São Sebastião |
| Map Alt: | Location of São Sebastião in Alagoas |
| Etymology: | Named in honor of the saint and governor at the time of the municipality's founding, Sebastião Muniz Falcão |
| Pushpin Map: | Brazil#South America |
| Pushpin Relief: | yes |
| Coordinates: | -9.9339°N -36.5444°W |
| Subdivision Type: | Country |
| Subdivision Name: |  Brazil |
| Subdivision Type1: | Region |
| Subdivision Type2: | State |
| Subdivision Name1: | Northeast |
| Established Title: | Founded |
| Established Date: | 31 May 1960[1] |
| Leader Title1: | Mayor |
| Leader Name1: | Jose Pacheco Filho (PP) (2021-2024)[2] |
| Leader Title2: | Vice Mayor |
| Leader Name2: | Charles Nunes Regueira (PP) (2021-2024) |
| Area Total Km2: | 314.924 |
| Elevation M: | 200 |
| Population As Of: | 2022 |
| Population Total: | 31786[3] |
| Population Density Km2: | 100.93 |
| Population Demonym: | Salomeense (Brazilian Portuguese) |
| Timezone: | Brasília Time |
| Utc Offset: | -03:00 |
| Postal Code Type: | Postal code |
| Postal Code: | 57275-000, 57279-000[4] |
| Blank Name: | HDI (2010) |
| Blank Info: | 0.549 – low |
| Website: | saosebastiao.al.gov.br |
São Sebastião is a municipality located in the Brazilian state of Alagoas. Its population was 34,290 (2020)[5] and its area is 306 km2.[6]