Résumé : Since the late 1990s, and particularly after the 2011 Arab Uprisings, many political actors classifiable as “Islamist” seem to have given up on their ideologies in order to enter into the rules of the liberal democracy. An interesting actor, protagonist of this phenomenon is the Tunisian political party Ennahda which, since its first origins in the late 1960s until 2016, has lived an extraordinary ideological transformation from being Islamist to Muslim Democrat.In order to explain the causes and the characteristics of the Ennahda’s ideological journey, this thesis uses as an analytical framework the Post-Islamist theory and the theoretical conception of ideology developed by Antonio Gramsci.By comparing every step of Ennahda’s history with the concepts of Islamism and Post- Islamism (mainly referring to Olivier Roy and Asef Bayat), this work demonstrates that the phenomenon occurring within Ennahda is a substantial and strategic shift characterised by the abandonment of Islamism towards Post-Islamism.This thesis explains that in the first movements at the origins of today’s Ennahda (Al- Jamaʿa al-Islamiyya, Al-Haraka al-Ittijah al-Islami and Al-Haraka al-Nahda) the category of Islamism is, in different measures, matched, since they all profess the willingness to build an Islamic state (al-dawla al-islāmiyya) based on shari‘a and give a strong role to daʿwa (preaching and spreading the call of Islam). The last Haraka al-Nahda and Hizb Haraka al- Nahda born in 2011, on the contrary, do not fit this Islamist paradigm since, starting from the late 2000s and in particular on the occasion of the 2011 Tunisian Uprising, they gave up to all these postulates in order to become a moderate and technocratic party.On this regard the work explains that these last decisions taken by Ennahda are substantial and strategic and bring it into a complete Post-Islamist stage.This research tries to give a clear answer to a much-debated phenomenon and can help the “navigation” in the very broad literature dealing concepts such as Islamism, Ennahda and the between Islam and politics.