Metrosideros polymorpha, the ʻōhiʻa lehua, is a species of flowering evergreen tree in the myrtle family, Myrtaceae, that is endemic to the six largest islands of Hawaiʻi. It is a member of the diverse Metrosideros genus, which are widespread over the southwest Pacific. It is the state tree of Hawai‘i.

Metrosideros is a genus of approximately 60 trees, shrubs, and vines mostly found in the Pacific region in the family Myrtaceae. Most of the tree forms are small, but some are exceptionally large, the New Zealand species in particular. The name derives from the Ancient Greek metra or "heartwood" and sideron or "iron". Perhaps the best-known species are the pohutukawa, northern and southern rātā of New Zealand, and ʻōhiʻa lehua, from the Hawaiian Islands.