I.O.IMain Vocalist

Sejeong

세정Kim Se-jeong (김세정)

I.O.I’s main vocalist and Produce 101 runner-up, whose work spans gugudan, solo songwriting and leading television roles.

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Source: I.O.I / Swing Entertainment

Age: 30; Aug 28, 1996
Height: 164 cm; 5′5″
MBTI: —
Debut: 2016; with I.O.I

At a glance

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Stage name: Sejeong (세정)
Birth name: Kim Se-jeong (김세정)
Position: Main Vocalist
Birthday: August 28, 1996 (age 30)
Zodiac sign: Virgo
Chinese zodiac: Rat
Height: 164 cm (5′5″)
Blood type: AB
Nationality: South Korean
Birthplace: Gimje, North Jeolla, South Korea
Joined: May 4, 2016

10 facts

About Sejeong

Sejeong finished second on Produce 101, sang with I.O.I and gugudan, and developed a solo career as a singer-songwriter. Her first studio album Door arrived in 2023 alongside her first solo concert tour. She also led Business Proposal, The Uncanny Counter and Moon River, and joined BH Entertainment in March 2026.

01
She appeared on K-pop Star 2 before joining Produce 101.
02
She grew up in Anyang after being born in Gimje.
03
She wrote and composed the B-sides of her first EP Plant and followed it with I’m in 2021.
04
She suggested the title Chrysalis for I.O.I’s debut EP.
05
She and Mina debuted with gugudan while still members of I.O.I.
06
Zico produced her 2016 solo single Flower Way.
07
She played Do Ha-na across both seasons of The Uncanny Counter.
08
School 2017 brought her a Best New Actress award at the KBS Drama Awards.
09
She made her straight-theatre debut in Temple after musical roles including Red Book.
10
She starred opposite Ahn Hyo-seop in Business Proposal and Kang Tae-oh in Moon River.

10 other members

Also in I.O.I

Full group profile

Photo credits

Mina at a Jongro fan signing in March 2017: SHAQ Photo · CC BY 4.0 · source