Armu (Russian: Арму) is a river in Krasnoarmeysky District of Primorsky Krai, a tributary of Bolshaya Ussurka River.
It is 201 km in length. The area of a river drainage basin is approximately 5424 km². The longest tributary of Armu is Obilnaya River (101 km).
The river is a popular place of tourism and fishing. One of sort of vodka named after it.