Bisei Observatory, Astronomical research center in Ibara, Japan

Bisei Observatory is an astronomical research center with a 101-centimeter telescope for observing stars, planets, and distant galaxies. The facility takes advantage of the dark and clear skies of Okayama Prefecture for its observation programs.

The observatory opened on July 7, 1993, as the symbol facility of Bisei Town's Leading Project, a revitalization plan themed on stars and the Middle Ages. The town had been formally designated for the project in March 1988. In 2005 the town merged into Ibara, and in 2021 the area was certified as a Dark Sky Community.

The observatory's home town, Bisei, was named for its clear starry skies, and in November 2021 the International Dark-Sky Association certified Bisei as a Dark Sky Community. Inside the building stands a full-scale replica of a Chinese armillary sphere, built and assembled in China from the original there.

The observatory is closed on Thursdays, the day after public holidays, and from December 29 to January 3. Daytime opening runs 9:30–16:00 on Tuesday and Wednesday and 13:45–16:00 on Friday, Saturday, Sunday and Monday; evening hours are 18:00–22:00 on those four days. From Yakage Station take the Hokushin bus to Bisei Shinryojo-mae and walk about 30 minutes.

The observatory holds a full-scale replica of a Chinese armillary sphere, built and assembled in China from the original there. The whole facility cost 458.4 million yen at construction, of which the telescope and dome took 143 million and the armillary sphere 15 million.