The essay describes the creation of a nationalistic ideology in the Illyric movement. It pays particular attention to the archetypal origin of Slavic, or perhaps Illyric ideology. The preface explains general theory of the myth's essence and its role in the European protonationalism in the first half of the 19th century. The authoress accentuates the fact that symbols and rituals, together with other forms of archetypal conduct, differ from other (medieval and ancient) manifestations of sacral life by their expressional interpretation and refinement. The first part of the essay deals with the myth's role in Croatian protonationalism and its link with the cultural collective identity of the Slavs. It exposes the terminological heterogeneity and mistaken identity of the terms Illyrian, Croatian and Slav, which was caused by an initial inaccuracy of the Slavic nationalistic conception. The second part is dedicated to the process of forming the South Slavs' ideology in connection with the practical side of their mother tongue, which was one of the most important forms of manifesting their national spirit. Upon the uneasy process of implementing Gaj's standard language form, it indicates the level of radius and popularity of Illyrism not only in its centre, i.e. the Croatian territory, but also beyond it, particularly in the Serbian and Slovenian space. The concept of Illyrism as a collective union of the Slavic entity followed pan-Slavic ideas of Croatian scholars in the first half of the 19th century. The closing part comments on their influence on the Illyrian movement, disputes concerning territorial boundaries of Great Illyria and searching for legitimacy of the term 'Illyrian' as a collective denomination of the South Slavs.