SIU

SIU may refer to:


 * Seafarers International Union of North America, an organization of labor unions
 * Segment of Independent Utility, a highway engineering term for divisions of large-scale construction projects; see
 * Shinawatra University, in Bangkok, Thailand
 * S.I.U. (film), a 2011 South Korean action film
 * SIU, a 2019 Vocaloid album
 * Siuna Airport in Nicaragua (IATA Code)
 * Slave In Utero, the pen name of Lee Jong-hui, author of the South Korean webcomic Tower of God
 * Southern Illinois University, a university system in the United States
 * Southern Illinois University Carbondale, the system's flagship university
 * Special Investigations Unit (Ontario), a police oversight agency in Ontario, Canada
 * Special Investigating Unit, South African law enforcement agency
 * Symbiosis International University, a private university in India

Siu may refer to:


 * Shao, a Chinese surname, sometimes transliterated as Siu
 * Siu, a god-hero of Torres Strait Islander people
 * Xiao (surname), a Chinese surname, sometimes transliterated as Siu

Siu may refer to in sport:
 * Siu (celebration) a celebration which has become increasingly popular and was made by Cristiano Ronaldo