cosmosy is a Japanese girl group under NTT Docomo Studio & Live and Sony Music Entertainment Korea. The group consists of four members, A'mei, Kamión, De_Hana and Himesha. They promote in Japan and South Korea.

Kamión and De_Hana were contestants on the Japanese reality survival show PRODUCE 101 THE GIRLS, placing 24th and 30th respectively.

The name cosmosy, is derived from the word “cosmos”, and the letter “y”, which is added as a symbol of youth and pure love, where the girls' will make the cosmos flower bloom in the world.

cosmosy debuted in Japan on December 31, 2024, later released a pre-debut song globally on February 5, 2025 with the digital single zigy=zigy.
On April 11, 2025, cosmosy made their official debut with the digital single Lucky=One.

On September 24, 2025, cosmosy released their first EP the a(e)nd, with all their previous releases added onto this EP along with three new songs.