Hilo (Hawaiian pronunciation: [ˈhilo]) is a census-designated place (CDP) and the largest city in Hawaii County, Hawaii, United States, which encompasses the Island of Hawaiʻi. The population was 43,263 according to the 2010 census.Hilo is the county seat of the County of Hawaiʻi and is in the District of South Hilo. The city overlooks Hilo Bay, at the base of two shield volcanoes, Mauna Loa, an active volcano, and Mauna Kea, a dormant volcano. Mauna Kea is the site of some of the world's most important ground-based astronomical observatories. Much of Hilo is at risk from lava flows from Mauna Loa, with the bay-front being twice destroyed by tsunamis. The majority of human settlement in Hilo stretches from Hilo Bay to Waiākea-Uka, on the flanks of the volcanoes.
Hilo is home to the University of Hawaiʻi at Hilo, ʻImiloa Astronomy Center, as well as the Merrie Monarch Festival, a week-long celebration of ancient and modern hula that takes place annually after Easter. Hilo is also home to the Mauna Loa Macadamia Nut Corporation, one of the world's leading producers of macadamia nuts. Hilo is served by Hilo International Airport.