Puu Kukui is a mountain peak in Hawaii. It is the highest peak of Mauna Kahalawai (the West Maui Mountains). The summit rises above the Puu Kukui Watershed Management Area, an private nature preserve maintained by the Maui Land & Pineapple Company. The peak was formed by a volcano whose caldera eroded into what is now the Iao Valley.
Puu Kukui is one of the wettest spots on Earth and the third wettest in the state after Big Bog, Maui and Mount Waialeale, receiving an average of of rain a year. Rainwater unable to drain away flows into a bog. The soil is dense, deep, and acidic.
Puu Kukui is home to many endemic plants, insects, and birds, including the greensword (Argyroxiphium grayanum), a distinctive bog variety of ōhia lehua (Metrosideros polymorpha var. pseudorugosa) and many lobelioid species. Due to the mountain peak's extreme climate and peat soil, many species, such as the ōhia, are represented as dwarfs. Access to the area is restricted to researchers and conservationists.