From its source on the Hakaru River, it flows generally south, with most of its length being through a drowned valley in the northeast of the Kaipara Harbour system.
The estuarine section of the river forms a part of the border between the Kaipara District of the Northland Region and the Rodney local board area of the Auckland Region.
The Topuni River flows into Oruawharo River — an arm of the Kaipara — 10 kilometres northwest of Wellsford.
"Place name detail: Topuni River".
This article about a river in the Northland Region is a stub.