Seidai Miyasaka
- All together with Hiroshi Abe
Seidai Miyasaka (宫 坂 正大jap, Miyasaka Seidai; * 1955) is a Japanese astronomer and discoverer of asteroids.
Together with his colleague Hiroshi Abe, he discovered the Yatsuka Observatory (IAU code 367) in Shimane prefecture between 1993 and 1997 a total of 4 asteroids.
The asteroid ( 3555 ) Miyasaka was named after him.