Seo Changbin (서창빈) is the main rapper of K-Pop group Stray Kids. He was born on August 11, 1999 in Yongin, South Korea, making him one of the older members of the group. Along with the main rapper position, he is also a vocalist and part of the producer line.

Changbin is a member of Stray Kids' pre-debut group 3RACHA that has shifted from a Soundcloud rap group to the unit that write and produce the majority of Stray Kids' music. His alias under this unit is “SpearB.”

Changbin is most known for his raspy tone and hard-hitting raps. He appeared on season 9 of Show Me The Money and released a “Cypher.” He also has a vocal track, “Streetlight,” which reaches out to people struggling with their mental health, referencing the Blue Tree Project.