The Opitonui River is a river of the Coromandel Peninsula in New Zealand's North Island. It flows north to reach the peninsula's east coast at Whangapoua Harbour, close to the small settlement of Te Rerenga. The river provides a water supply for Matarangi by way of a pipe laid across the Whangapoua harbour.

• List of rivers of New Zealand

"Place name detail: Opitonui River". New Zealand Gazetteer. New Zealand Geographic Board. Retrieved 12 July 2009.

36°45′S 175°37′E