This thesis explores the Twitter discourse surrounding French secularism, referred to as laïcité, and its interplay with Islam in France. The research aims to provide an in-depth synchronic analysis of patterns and Twitter users’ language and rhetoric when discussing the principle. Moreover, it attempts to examine the variations of these discussions based on their contextual relevance and Twitter’s algorithm. To achieve this, I conducted a Critical Discourse Analysis on three data sets containing the hashtag #laïcité and pertaining to discussions on France and Islam: The first set is a compilation of tweets from the 26th of March to the 1st of April 2023; the second set is a compilation of tweets following the Charlie Hebdo attacks, from the 8th of January to the 14th of January 2015; and the third set is a compilation of “Top Tweets” initiated by Twitter’s algorithm retrieved on the 4th of May 2023. The findings show a frequent instrumentalisation of laïcité to place the principle in elite and ideological discourses, discriminating against French Muslims. I identify two common discourses on #laïcité. First, laïcité is often associated with conservative France and is employed as a justification for propagating hate speech towards Islam and Muslims, especially on Twitter, where the platform's features and algorithm amplify this negative rhetoric. Second, laïcité is viewed as a critical aspect of French identity that frames the assimilation of French Muslims as the only way to comply with this principle.