"OPO" or "Opo" can refer to:
- Optical parametric oscillator
- OPO is the IATA airport code of Francisco de Sá Carneiro Airport, Porto, Portugal
- Organ procurement organization, which helps to arrange organ donation
- One Person Operation, a term used in road passenger transport where a driver of a vehicle has sole responsibility for operating the vehicle and passenger interaction. The opposite of the earlier two-person operation system where the vehicle operation and passenger interaction roles (for example, driver and conductor) were separate and distinct.
- Opo is a common name for the squash species Lagenaria siceraria
- Opo the Dolphin was the name of a famous dolphin in New Zealand
- Online Presence Ontology
- Orlando Philharmonic Orchestra
- Ovamboland People's Organization the predecessor of SWAPO
- OnePlus One, a smartphone model produced by the Chinese company OnePlus.
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 after her mother had been killed, and would swim daily in the bay close to town. 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.
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, but on 9 March she was found dead in a rock crevice at Koutu Point. There were suggestions that she had become stranded while fishing, or that she had been killed by fishermen fishing with gelignite. Her death was reported nationwide, and she was buried with full Māori honours in a special plot next to the War Memorial Hall.