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.