Kōichi Itagaki

is an amateur astronomer based in Yamagata, the capital city of Yamagata Prefecture in the Tōhoku region of northern Honshu island, Japan. He is responsible for discovering many comets, and over 170 supernovae.

Early life Itagaki had an early fascination with lenses, and used them to burn paper with concentrated sunlight.

In 1963, the 19-year-old Japanese amateur Kaoru Ikeya created national headlines when he discovered a comet with his homemade telescope. Itagaki was thus encouraged and bought a telescope and, after completing highschool, discovered a comet himself at age 20. . As of late-2024, Itagaki's most recent discovery is: SN 2024abfl.

Recognition Asteroid 1997 UN8 (/List of minor planets: 14001–15000) was named in his honour.

In 2009, he received the Edgar Wilson Award from the International Astronomical Union for the discovery of comet C/2009 E1.

On 22 May 2023, supernova SN 2023ixf in the M101 galaxy, discovered by Itagaki three days previously, was featured on NASA's Astronomy Picture of the Day.