| Mouth location | Iller |
|---|---|
| Mouth coordinates | 47.4273°N 10.274°E |
| Country | Germany |
| State | Bavaria |
| Length | 15.6 km |
| Basin size | 157 km² |
Trettach is a river of Bavaria, Germany. At its confluence with the Breitach and the Stillach in Oberstdorf, the Iller is formed.