| Official Name: | Decker, Montana |
| Pushpin Map: | Montana#USA |
| Subdivision Type: | Country |
| Subdivision Name: | United States |
| Subdivision Type1: | State |
| Subdivision Name1: | Montana |
| Subdivision Type2: | County |
| Subdivision Name2: | Big Horn |
| Population Total: | 76 |
| Timezone: | Mountain (MST) |
| Utc Offset: | -7 |
| Timezone Dst: | MDT |
| Utc Offset Dst: | -6 |
| Elevation Ft: | 3524 |
| Coordinates: | 45.0119°N -106.8633°W |
| Postal Code Type: | ZIP code |
| Postal Code: | 59025 |
| Area Code: | 406 |
| Blank Name: | GNIS feature ID |
| Blank Info: | 770540 |
Decker is an unincorporated community in Big Horn County, Montana, United States.
The community is located along Secondary Highway 314, 15.5miles north-northeast of Sheridan. Decker has a post office with ZIP code 59025.[1] The community is home to a one-room public school, the Spring Creek School; it has nine pupils and is one of 200 remaining one-room public schools in the United States.[2]
In the late 1930s, the State Water Conservation Board constructed the Tongue River Dam, creating a reservoir just north of Decker.[3]
According to the Köppen Climate Classification system, Decker has a semi-arid climate, abbreviated "BSk" on climate maps.[4]