The river system that includes the Argun River and flows to the Sea of Okhotsk is the Amur system.
The Amur begins where the Shilka and Argun meet near the Russia–China border. From there it flows generally east and northeast, forming part of the border between Russia and China before reaching the Strait of Tartary and the Sea of Okhotsk. When the Argun is counted as the upstream branch, the Amur system is more than 4,400 kilometres long.
The Argun itself forms a substantial section of the China–Russia boundary and joins the Shilka to create the Amur proper. Another possible extended measurement includes the Kherlen River, which can connect through Hulun Lake during unusually wet conditions; that produces a longer Kherlen–Argun–Amur system. In ordinary river questions, however, “Amur” is the canonical name for the system described.