Nāʻālehu (Hawaiian: Nāʻālehu) is a community in Hawaiʻi County, Hawaii, United States. Nāʻālehu is Hawaiian for "the volcanic ashes". It is the southernmost community with a post office in the 50 states of the United States. (See List of extreme points of the United States.) For statistical purposes, the United States Census Bureau has defined Naalehu as a census-designated place (CDP). The census definition of the area may not precisely correspond to local understanding of the area with the same name. The population was 866 at the 2010 census, down from 919 at the 2000 census.
Nāʻālehu is located near the southern tip of the island of Hawaiʻi at 19°3′57″N 155°35′15″W (19.065925, -155.587528) in the Kaʻū District. It is bordered to the west by Waiohinu, and Discovery Harbour is to the southwest. (The two communities are census-designated places but do not have post offices.)
According to the United States Census Bureau, the Nāʻālehu CDP has a total area of 2.2 square miles (5.6 km2), all of it land.
As of the census of 2000, there were 919 people, 290 households, and 209 families residing in the CDP. The population density was 426.1 people per square mile (164.3/km²). There were 332 housing units at an average density of 153.9 per square mile (59.3/km²).