| Hario | |
| Native Name: | Japanese: 針尾島 |
| Map: | Japan |
| Location: | Ōmura Bay |
| Area Km2: | 33.16 |
| Length Km: | 10 |
| Width Km: | 6 |
| Coastline Km: | 63 |
| Elevation M: | 174 |
| Country: | Japan |
| Country Admin Divisions Title: | Sasebo |
| Country Admin Divisions: | Nagasaki Prefecture |
| Population: | 9767 |
| Population As Of: | 2015 |
| Density Km2: | 295 |
| Ethnic Groups: | Japanese |
, is a large island located in the mouth of Ōmura Bay, part of the Nagasaki Prefecture, Japan. It is the 7th largest and 6th most populous island of the islands in Nagasaki Prefecture. The island, 33.16 km² in area, had 9767 inhabitants . The island is dominated by the Citrus unshiu plantations.The island access is by road and rail transport from the mainland of Kyushu through seven bridges linking it to Sasebo and Saikai cities. The main access routes are Japan National Route 202 and Japan National Route 205.
The Hario island is composed of rhyolite lava flows, resulting in very irregular coastline, except of north-eastern portion where the smoother tidal channel approximately 100 m wide separate Hario island from the Kyushu island. The heavily eroded lava plateau is mostly unsuitable for rice agriculture, with the island dominated by the Citrus unshiu orchards instead. The northern part of the island is hilly, forming an intricate valley network. The bay on the northern tip of the island houses US military station. The housings are concentrated on the north-east, along the tidal channel.
Up to Jōmon period the obsidian commonly found on the Hario Island was an important raw material for the stone tools. Later, an attempt was made to make porcelain using a local rhyolite outcrops, but was abandoned. Following a severe power struggle between Ōmura Domain and Hirado Domain during Sengoku period, the island was eventually absorbed into Hirado Domain and development resumed. Thanks to the shallow sea around, land reclamation was extensive starting from the Edo period. By the end of Edo period, the island housed a Smoke signal station to notify Hirado Island of the passage of the Dutch merchants to the Dejima. In 1936, the has connected Hario island to the Saikai city, putting the end to the ferry operations.
Currently islanders are focusing on citrus unshiu, livestock breeding and cultured pearl production, and small scale fishing too to earn a living.