Surname Сиюнь (Xiyun 
, Сиюнь 
) , in all the world, is a very rare cognomen. The surname Сиюнь is characteristic of Finland, where it is a very rare surname, Malaysia, where it is an extremely rare surname, and Chile. In absolute terms, it is the most numerous in China, Finland, and the United States. Predominantly, Сиюнь is the forename as well as the last name.