| Koiwai Station | |
| Style: | JR East |
| Native Name: | 小岩井駅 |
| Native Name Lang: | ja |
| Address: | 19-2 Ogamafurin 19-2, Takizawa-shi, Iwate-ken 020-0757 |
| Country: | Japan |
| Operator: | JR East |
| Line: | Tazawako Line |
| Platforms: | 2 side platforms |
| Tracks: | 2 |
| Distance: | 10.5 km from |
| Structure: | At grade |
| Status: | Unmanned station |
| Opened: | June 25, 1921 |
| Passengers: | 496 |
| Pass Year: | FY2015 |
| Map Type: | Japan |
is an East Japan Railway Company (JR East) railway station located in the city of Takizawa, Iwate Prefecture, Japan.
Koiwai Station is served by the Tazawako Line, and is located 10.5 km from the terminus of the line at Morioka Station.
Koiwai Station has a two opposed side platforms, connected to the wooden station building by a footbridge. The station is Unmanned.
Koiwai Station opened on June 25, 1921. The station was absorbed into the JR East network upon the privatization of the JNR on April 1, 1987.
In fiscal 2015, the station was used by an average of 496 passengers daily (boarding passengers only).[1]