Lyon Arboretum is a 200-acre botanical garden and arboretum at the upper end of Mānoa Valley in Honolulu, managed by the University of Hawaiʻi at Mānoa. Founded in 1918 by the Hawaiian Sugar Planters' Association as the Manoa Arboretum, it was created to demonstrate watershed restoration, test trees for reforestation, and gather economically useful plants. Its first director, Dr. Harold L. Lyon, planted nearly 2,000 tree species, and the site was transferred to the university in 1953 and later renamed for him after his death in 1957. Today it holds more than 15,000 accessions and supports major native plant conservation through its Seed Conservation Laboratory.