| Official Name: | Big Island Township, Ohio |
| Settlement Type: | Township |
| Mapsize: | 250px |
| Subdivision Type: | Country |
| Subdivision Name: | United States |
| Subdivision Type1: | State |
| Subdivision Name1: | Ohio |
| Subdivision Type2: | County |
| Subdivision Name2: | Marion |
| Unit Pref: | Imperial |
| Area Total Km2: | 91.4 |
| Area Land Km2: | 91.3 |
| Area Water Km2: | 0.0 |
| Area Total Sq Mi: | 35.3 |
| Area Land Sq Mi: | 35.3 |
| Area Water Sq Mi: | 0.0 |
| Population As Of: | 2020 |
| Population Footnotes: | [1] |
| Population Total: | 1174 |
| Population Density Km2: | auto |
| Population Density Sq Mi: | auto |
| Timezone: | Eastern (EST) |
| Utc Offset: | -5 |
| Timezone Dst: | EDT |
| Utc Offset Dst: | -4 |
| Elevation Footnotes: | [2] |
| Elevation M: | 277 |
| Elevation Ft: | 909 |
| Coordinates: | 40.6083°N -83.2378°W |
| Blank Name: | FIPS code |
| Blank Info: | 39-06348[3] |
| Blank1 Name: | GNIS feature ID |
| Blank1 Info: | 1086574 |
Big Island Township is one of the fifteen townships of Marion County, Ohio, United States. The 2020 census found 1,174 people in the township.
Located in the western part of the county, it borders the following townships:
No municipalities are located in Big Island Township.
Big Island Township was established in 1823, and named for a tract of forest early settlers believed must have been located on an island.[4] It is the only Big Island Township statewide.
The township is governed by a three-member board of trustees, who are elected in November of odd-numbered years to a four-year term beginning on the following January 1. Two are elected in the year after the presidential election and one is elected in the year before it. There is also an elected township fiscal officer,[5] who serves a four-year term beginning on April 1 of the year after the election, which is held in November of the year before the presidential election. Vacancies in the fiscal officership or on the board of trustees are filled by the remaining trustees.