Acacia koa is a species of flowering tree in the pea family, Fabaceae. It is endemic to the Hawaiian Islands, where it is the second most common tree. The highest populations are on Hawaiʻi, Maui and Oʻahu. Its name in the Hawaiian language, koa, also means brave, bold, fearless, or warrior.

The koa's trunk was used by ancient Hawaiians to build dugout outrigger canoes and surfboards. The reddish wood is very similar in strength and weight to that of Black Walnut (Juglans nigra), with a specific gravity of 0.55, and is sought for use in wood carving and furniture. Koa is also a tonewood, often used in the construction of ukuleles, acoustic guitars, and Weissenborn-style Hawaiian steel guitars.

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