Puʻu ʻŌʻō (often written Puu Oo, and pronounced [ˈpuʔu ˈʔoːʔoː] is a volcanic cone in the eastern rift zone of the Kīlauea volcano of the Hawaiian Islands. Puʻu ʻŌʻō has been erupting continuously since January 3, 1983, making it the longest-lived rift-zone eruption of the last two centuries.
By January 2005, 2.7 cubic kilometers (0.65 cu mi) of magma covered an area of more than 117 square kilometers (45 sq mi) and added 230 acres (0.93 km2) of land to the Southeast coast of Hawaiʻi. So far, the eruption has claimed 189 buildings and 14 kilometers (8.7 mi) of highways, as well as a church, a store, the Wahaʻula Visitor Center, and many ancient Hawaiian sites, including the Wahaʻula heiau. The coastal highway has been closed since 1987, as it has been buried under lava up to 35 meters (115 ft) thick.
The hill was initially nicknamed "Puʻu O" by volcanologists, as its position when marked on a map of the area coincided with an "o" in "Lava flow of 1965". Later, the elders of the village of Kalapana were asked to name the new hill, and chose Puʻu ʻŌʻō, meaning hill of the digging stick. The name is also often translated as "Hill of the ʻŌʻō Bird".