Kim Si-yoon
- Born
- 16 February 2005 (21 years)
- Place of birth
- Seoul, South Korea
- Gender
- Female
Kim Si-yoon, known mononymously as Siyoon, is a South Korean rapper, singer and lyricist under MYSTIC STORY. She is a member of the girl group Billlie and its sub-unit Moon Sua X Siyoon.
