Ennik Somi Douma/Somi - Lead Dancer, Lead Vocalist, Rapper, Face of the Group, Center, & Maknae (Dutch/Korean/Canadian) [01'liner] {subunit: I.O.I. subunit}(currently: a soloist)
Kim Chanmi/Chungha - Main Dancer, Lead Vocalist, & Rapper (South Korean) [96'liner] {subunit: I.O.I. subunit} (currently: soloist)
Kim Doyeon - Sub Vocalist (South Korean) [99'liner] {subunit: I.O.I. subunit} (currently: in Weki Meki)
Zhou Jieqiong/Kyulkyung - Lead Dancer, Vocalist, & Visual (Chinese) [98'liner] {subunit: I.O.I. subunit} (currently: in Pristin which has disbanded)
Kim Sejeong - Main Vocalist (South Korean) [96'liner] (currently: in Gugudan which has disbanded)
Choi Yoojung - Lead Rapper, Lead Dancer, & Lead Vocalist (South Korean) [99'liner] {subunit: I.O.I. subunit} (currently: in Weki Meki)
Kim Sohye - Vocalist & Rapper (South Korean) [99'liner] {subunit: I.O.I. subunit} (currently: an actress)
Jung Chaeyeon - Vocalist & Visual (South Korean) [97'liner](currently: in DIA)
Kang Mina - Lead Dancer, Vocalist, & Rapper (South Korean) [99'liner] (currently: in Gugudan which has disbanded)
Im Nayoung - Leader, Main Rapper, Lead Dancer, & Vocalist (South Korean) [95'liner] {subunit: I.O.I. Subunit} (currently: in Pristin which has disbanded)
Yu Yeonjung - Main Vocalist (South Korean) [99'liner] (currently: in Cosmic Girls)
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Years active: 2016 - 2017
Entertainment: YMC Entertainment and CJ E&M (formerly), Studio Blu (currently)