In November 2015, Mnet announced their new survival show that would bring together 101 trainees from 46 entertainment companies to form a unit girl group with eleven members chosen by the viewers.

[15] I.O.I officially debuted on May 4, 2016, through the release of their first album, Chrysalis, accompanied with a music video for the title track "Dream Girls".

The song is a trap pop dance track co-written by Eru and Paul with rap lyrics written by members Lim Na-young and Choi Yoo-jung.

The title track, "Very Very Very", was written, composed and arranged by Park Jin-young, founder of Jeon So-mi's agency JYP Entertainment.

[36][37][38] On January 17, YMC Entertainment announced that the group's final track before official disbandment would be "Downpour", written and co-produced by Seventeen's Woozi.

[42][43] The band officially disbanded on January 29, with the members' last television show appearance on MBC's Section TV and the fan cafe closing down on the 31st.

[46] On July 1, 2019, Studio Blu confirmed that the group would return in October 2019 with nine members, excluding Yoo Yeon-jung and Jeon So-mi.

[49] On October 29, the comeback was canceled due to scheduling conflicts between the members and the ongoing Mnet vote manipulation investigation.

[52] It was reported on March 24, 2016, that even before the finale of Produce 101, the group already confirmed seven CF deals for different companies with an estimated profit of ₩1.4 billion.

[91] On April 4, 2016, I.O.I was appointed as new model for Etude House, Mom's Touch Chicken and Burger, Woongjin Foods' Haneul Bori Ice Sparkling Water and HiteJinro's Chamisul.

[92] However, due to the legal drinking age in South Korea, only three members, Lim Na-young, Chungha and Kim Se-jeong, were involved in filming of the ad for a new alcoholic beverage by distiller HiteJinro.