| Full Name | Park Si-eun |
| Stage Name | Sieun |
| Native Name | 박시은 |
| Birthday | August 1, 2001 |
| Age | 23 years and 11 months old |
| Zodiac Sign | Leo |
| Birthplace | Ichon-dong, Yongsan-gu, Seoul, South Korea |
| Height | 5’3″ (159 cm) |
| Weight | 97-101.4 lbs44-46 kg |
| Blood Type | A |
| MBTI | ENFJ |
| Education | Chung-Ang University College of Arts |
| Languages | Korean, English, Japanese |
| Group | STAYC (2020-present) |
| Social Media | Instagram: [@hermesieunn] |