Oka-dera (岡寺) is a Buddhist temple located in the Oka neighborhood of the village of Asuka, Nara Prefecture, Japan.

According to the "Gien-den" in the "Tōdaiji Yoroku" and the "Fusō Ryakuki", the temple was founded when the monk Gien (643-728) built a building on the site of the Okamiya Palace, the residence of Prince Kusakabe, the son of Emperor Tenmu who died in 689.

According to the temple's legend, Gien sealed an evil dragon which had been tormenting the local residences in a pond and covered it with stones.

Gien was the founder of the Hosso sect, and his disciples included Rōben and Gyōki, who were involved in the founding of Tōdai-ji.

The Kaisan-dō (Founder's Chapel) dates from 1797 and was relocated to Oka-dera in 1871 from Myōraku-ji (Tanzan Shrine) due to the Meiji government's edicts separating Buddhism from Shinto.