| Iso-Vietonen | |
| Pushpin Map: | Finland Lapland |
| Location: | Ylitornio |
| Coords: | 66.6168°N 24.6323°W |
| Type: | Lake |
| Inflow: | Jolmankoski |
| Outflow: | Kaaraneskoski |
| Catchment: | Tornionjoki |
| Basin Countries: | Finland |
| Area: | 35.377km2 |
| Depth: | 6.36m (20.87feet) |
| Max-Depth: | 20.39m (66.9feet) |
| Volume: | 0.225km3 |
| Shore: | 51km (32miles) |
| Elevation: | 91.8m (301.2feet) |
| Frozen: | December–May |
| Islands: | Himotussaari, koivusaari |
Iso-Vietonen is a medium-sized lake in the Tornionjoki main catchment area. It is located in Ylitornio municipality, in the Lapland region in Finland.[1]