Iran used to be called Persia ( for a long time by people outside of Iran ) . The name `` Iran '' has been in use natively since the Sassanian era and came into use internationally in 1935 , before which the country was known to the western world as Persia . Both `` Persia '' and `` Iran '' are used interchangeably in cultural contexts ; however , `` Iran '' is the name used officially in political contexts .