Which K-Pop group had the very first foreign member (Chinese)?

Super Junior had K-pop’s first Chinese foreign member, Han Geng. He was recruited by SM Entertainment in Beijing in 2001 and later debuted with Super Junior 05 in 2005.

Han Geng’s addition was significant because Korean idol groups were still overwhelmingly made up of Korean members. SM Entertainment discovered him through an overseas audition reportedly attended by about 3,000 applicants. After moving to South Korea, he trained in singing, dancing, acting, and Korean language skills.

Han Geng was initially one of Super Junior’s original members and later became the leader of Super Junior-M, the group’s Mandarin-focused sub-unit. Super Junior-M debuted in China in 2008 and helped establish a stronger connection between K-pop and the Chinese market.

A common mix-up is confusing the first foreign member with the first non-Korean idol overall. The wording here specifically points to a Chinese member in a K-pop group, making Super Junior the accepted answer.