Cho Ha-seul (Korean: 조하슬; born August 18, 1997), mononymously known as HaSeul (하슬), is a South Korean singer under MODHAUS. She is the third revealed member of girl group LOONA (Hangul: 이달의 소녀), and its first sub-unit LOOΠΔ 1/3. She is also a member of girl group ARTMS. She debuted as a LOONA member on December 15, 2016 with the solo single album HaSeul. On October 26th, 2023 she released special single "Plastic Candy" in support of her theatre concert.