Choi Taeyang (최태양; born Jul 1, 2001) better known by his stage name Theo (테오), is a South Korean singer and member of the Kpop group P1Harmony under FNC Entertainment. Theo debuted with P1Harmony on October 28, 2020. Theo was born on July 1, 2001, in Daejeon, South Korea. He is the only child and his mother is a hairstylist. He attended Karma Middle School and graduated from Hanbat High School. He attended Daejeon Dance and Vocal Academy, the same academy that JUST B's Geonu and WEI's Seokhwa attended. He joined FNC Entertainment in 2018 and trained for 1 year and a half before debut. Prior to joining FNC Entertainment, Theo was a trainee at SM Entertainment. In 2019, Theo as well as other FNC trainees, artist and employees traveled to Mongolia on the “LOVE FNC 5th Volunteer Team”, as part of FNC Entertainment’s charity program. On September 3, 2020, Theo was introduced as the second member of P1Harmony, and is known mainly as one of the vocalists of the group, but is often mentioned as one of the visual members as well. He participated in writing many P1Harmony’s songs “Intro; Breakthrough (틀)”, “That’s It (이거지)” and ” Breakthrough (틀) (Full Version)” along with Keeho.