| Mirna | |
| Mouth Location: | Adriatic Sea |
| Mouth Coordinates: | 45.3164°N 13.5948°W |
| Subdivision Type1: | Country |
| Subdivision Name1: | Croatia |
| Length: | 53km (33miles) |
| Basin Size: | 458km2 |
The Mirna (Italian: Quieto) is a river in Istria, Croatia. In ancient times it was called the Aquilis. It is Istria's longest and richest river, being 53km (33miles) long and having a basin covering an area of 458km2. It rises near Buzet, passes along Motovun and empties into the Adriatic Sea near Novigrad.[1]