Since the early 2010s, French politicians have steadily utilized Twitter as a communication tool. Political tweets about immigration are prolifically produced by Marine Le Pen (former leader of the French far-right populist Party Rassemblement National). Their biased social representation of migrants, immigrants, and asylum seekers seems to be instilled in manifold voters through online public debate and media. To characterize political immigration discourse on Twitter, we developed, within the framework of the research project OLiNDiNUM (Observatoire Linguistique du discours numérique [Linguistic Observatory of Online Discourse]), the diachronic bilingual corpus of political tweets posted throughout the last 12 years, from 2011 to 2022. The whole MigrTwit corpus consists of three subcorpora, for a total of 23869 tweets, with 703016 words. The constitution of the French MigrTwit corpora enabled us to study the evolution of immigration discourse in comparative and corpus-based approaches. In: Proceedings of the 10th International Conference on CMC and Social Media Corpora for the Humanities (CMC-Corpora 2023), 14–15 September 2023, University of Mannheim, Germany, pp. 108-111.