Yoo Yeon-jung (Hangul: 유연정; Hanja: 兪延靜; born August 3, 1999), better known by the mononym Yeonjung, is a South Korean singer. She is best known for being a member of the South Korean girl group Cosmic Girls, and for finishing 11th in the survival show Produce 101, making her a member of I.O.I.
Yeon-jung, together with Kim Tae-ha and Shim Chae-eun represented Starship Entertainment in the Mnet reality-survival program Produce 101 which aimed to form an eleven-member girl group that will promote for a year under YMC Entertainment. Yeon-jung placed 11th with a total of 136,780 votes in the final episode and debuted as a member of I.O.I while the other 2 trainees were eliminated.
On May 4, project girl group I.O.I debuted with the mini-album Chrysalis.
After the disbandment of I.O.I, Yeon-jung was introduced as the thirteenth member of Cosmic Girls.
Yeon-jung also made her acting debut, making a cameo in A Korean Odyssey.