- Name: Eguchi Saya (江口紗耶)
- Birthday: August 1, 2003
- Birthplace: Hyogo, Japan
- Blood Type: O
- Height: 150cm
- Specialty: Dance, piano, back bridge
- Hobbies: Playing musical instruments, singing songs
- Looks Up To: Suzuki Airi
- Hello! Project groups:
- Hello! Pro Kenshuusei (2017–)
- Unnamed Group (2018–)
Eguchi Saya first appeared as a member of Hello Pro Kenshuusei on March 6, 2017 in an announcement on the official website, alongside Shimakura Rika, Hibi Marina, Doi Rena, Okamura Minami, Matsunaga Riai, Yamada Ichigo, and Nakayama Natsume. She made her first live appearance and was formally introduced at the "Hello Pro Kenshuusei Happyoukai 2017 3gatsu ~Marching!~" event on March 11, 2017.
On June 9, 2018 during the "Hello! Project Kenshuusei Happyoukai 2018 6gatsu ~Niji~" event in Tokyo, it was announced that Eguchi would join the upcoming group featuring previously announced leader Ichioka Reina, along with Nishida Shiori and Shimakura Rika. The group would be unveiled at a later date in 2018.
- Her favorite genres of music are J-Pop and western music.
- Favorite sports are tennis and badminton.
- Favorite foods are macaroons, mont blanc, buri and hamachi
- Her motto is "Hard work opens all doors" (努力は全ての扉を開く).
- Thinks her charm point is her long curled eyelashes.
- Her favorite school subject is physical education.
- Her favorite color is dark pink.
- She can dance the samba.
- Shares a birthday with Hello! Project and ANGERME Leader, Wada Ayaka.