The Luxembourgish sociolinguistic context, structured around a pluriglossy inscribed diachronically in a secular history, calls for specific language arrangements for the purpose of addressing a particular demographic situation in which nearly 50% of residents are foreign nationals. Varieties imported by foreigners are combined with this historical national trilingualism and widely disseminated within the economic sphere.The first part of this thesis therefore lists the conditions for the existence of a “language policy” according to a historical and geographical context that justifies the presence of linguistic varieties in a given territory. It is intended to base a definition of these varieties on three perspectives: a morphological perspective, a symbolic perspective, and a sociological perspective. Language, seen as a component of a linguistic ecology – according to Einar Haugen –, involves complex political and social arrangements that govern its management according to its propagation environment. The descriptive analysis then focuses on the study of these organisational systems of planning or development, which are translated into national language policies.The second part focuses on current language policies in Luxembourg, which are strained between the dual objective of promoting the national variety, Luxembourgish, and of attracting, by economic necessity, a massive workforce divided into two major groups: French speakers and English speakers. The analysis is based on a double corpus consisting, on the one hand, of a collection of interviews conducted with actors involved in the implementation of these local language policies, and on the other hand, a collection of questionnaires distributed to a sample of foreigners residing and working in the country. Their study reveals a complex sociolinguistic situation which disrupts the hierarchical ranking of the three national languages - French, German and Luxembourgish. The successive linguistic arrangements attempt to reconcile these antagonisms by ...