Rainier
- County:
- Columbia County
- County Seat:
- No
- Area (mi²):
- 4.081
- State:
- Oregon
Rainier is a city located in Columbia County, Oregon. Rainier has a 2026 population of 1,932. Rainier is currently growing at a rate of 0.21% annually and its population has increased by 1.31% since the most recent census, which recorded a population of 1,907 in 2020.