Puʻu ʻŌʻō, Volcanic cone in Hawaii County, United States.

Puʻu ʻŌʻō is a 698-meter-high cinder and spatter cone on Kīlauea's eastern rift zone, built by lava fountains during the eruption that began on January 3, 1983. Prevailing winds piled ejected material mainly on its southwest side, making the cone markedly asymmetrical. Its summit is notched, and its slopes are made of black, jagged ʻaʻā rock.

The eruption that built Puʻu ʻŌʻō started on 3 January 1983, when fissures opened in the Nāpau Crater area of Hawaiʻi Volcanoes National Park. By June 1983 activity had focused on the vent, and 44 episodes of fountaining up to 460 m high built a 255 m cinder-and-spatter cone. In July 1986 the conduit ruptured and the eruption shifted 3 km downrift to Kūpaʻianahā; activity returned to the cone's flank vents in 1992 and continued until 30 April 2018.

The name Puʻu ʻŌʻō was chosen by elders of Kalapana, meaning "hill of the digging stick" — the pāoa staff with which the goddess Pele is said to create volcanoes; it is also translated as "Hill of the ʻŌʻō Bird". Volcanologists had first nicknamed the hill "Puʻu O" after an "o" on a 1965 lava-flow map. In 2021 the Hawaiʻi Board of Geographic Names set the spelling Pu‘u‘ō‘ō.

The cone sits inside Hawaiʻi Volcanoes National Park, but the coastal highway it buried has been closed since 1987, with lava up to 35 m thick over parts of the road. Access is on foot over old flows; check current eruption and closure status with the park before setting out. The 2018 collapse left the crater floor altered, so route-finding is not straightforward.

The name was a stopgap: volcanologists nicknamed the hill "Puʻu O" because its map position matched an "o" in the label "Lava flow of 1965". Elders of Kalapana were then asked to name it and chose Puʻu ʻŌʻō, "hill of the digging stick", also read as "Hill of the ʻŌʻō Bird". In 2021 the Hawaiʻi Board of Geographic Names respelled it Pu‘u‘ō‘ō.