The research on collective actants is mainly concerned with the effects of the meaning of their compositions and their metamorphoses. Their evolutions, and notably the actantial roles they play, are mainly on the political dimension of social interactions, depend primarily on these modes of composition, and more precisely on what constitutes the moment of unity of the composition; in other words, the link that gives them a durable identity, and that allows them to resist, to persist, and to face the risks of existence. One of these moments of unity is the result of a mythification of the actantial composition: this composition seems to be founded on an origin which has the shape of a myth. Some of these constitutive myths are manifested by one or more passions: the moment of unity and the identity of the collective actant then comprise the elements necessary for semiosis: the mythical structure on the side of semiotic immanence and the passionate expression on the side of manifestation. My proposal concerns precisely the definition, the analysis, and the exemplification of these “passion-myths” constitutive of collective actants.