Izunagaoka (伊豆長岡町, Izu-Nagaoka-chō) was a town located in Tagata District, Shizuoka Prefecture, Japan in northern Izu Peninsula.

Izunagaoka 伊豆長岡町
Former municipality
Flag Emblem
Location of Izunagaoka in Shizuoka Prefecture
Izunagaoka Location in Japan
Coordinates: 35°02′24″N 138°56′51″E / 35.0399°N 138.9475°E / 35.0399; 138.9475
Country	Japan
Region	Chūbu (Tōkai)
Prefecture	Shizuoka Prefecture
District	Tagata
Merged	April 1, 2005 (now part of Izunokuni)
Area
• Total	16.52 km2 (6.38 sq mi)
Population  (April 1, 2005)
• Total	15,339
• Density	928.5/km2 (2,405/sq mi)
Time zone	UTC+09:00 (JST)
Symbols
Bird	Japanese white-eye
Flower	Iris
Tree	Osmanthus

As of March 1, 2005, the town had an estimated population of 15,339 and a density of 928.5 persons per km². The total area was 16.52 km². The town was served by a station on the Izuhakone Railway.

On April 1, 2005, Izunagaoka, along with the towns of Nirayama and Ōhito (all from Tagata District), was merged to create the city of Izunokuni and thus it no longer exists as an independent municipality.

Izu-Nagaoka was established on April 1, 1889 as Kawanishi Village. It was renamed Izunagaoka Town on November 3, 1934.