Opo was a bottlenose dolphin who became famous throughout New Zealand during the summer of 1955/56 for playing with the children of the small town of Opononi on the Hokianga harbour.

Opo was a wild dolphin that started following fishing boats around Opononi in early 1955. She was originally named "Opononi Jack", based on Pelorus Jack, since she was presumed to be male. Unlike the majority of dolphins, she had no qualms about human company, and would perform stunts for locals, play with objects like beach balls and beer bottles, and allow children to swim alongside her and make contact.

Māori children were more reluctant to play with Opo, as cultural beliefs said the dolphin was a messenger from Kupe. (Kupe was a legendary Polynesian explorer, navigator and great rangatira of Hawaiki, who is said to have been the first human to discover New Zealand)

The dolphin became a local celebrity but news of her soon spread, and visitors from throughout the country would come to watch her. On 8 March 1956 official protection for Opo, requested by locals, was made law.