This thesis is a qualitative sociolinguistic study of multilingualism and multilingual practices in the country of Luxembourg. Multilingualism is studied as a natural human state or phenomenon, which allows for a deeper understanding of underlying social structures in a given society. The research is based on five approximately one-hour long sociolinguistic interviews with respondents of different nationalities who are long-term residents in Luxembourg, which means that they have been living there for more than six months. The respondents include a Luxembourgish high-school student, a Kuwaiti student at university, a Portuguese official at the European Parliament, a Hungarian head of service at the European Parliament and a Danish translator at the European Parliament. The diversity of the respondents is meant to represent the diversity of the Luxembourgish society and their answers highlight and expose experiences, practices and conflicts which are not visible from the dominant perspective of the idealistic trilingualism. This view focuses on French, German and Luxembourgish and on the portion of the population which speaks these three languages, while marginalizing many recent and historical changes in population structure and the organization of the professional and public sphere in Luxembourg. The aim of this thesis is to expand the observation of multilingualism in Luxembourg to the relevant social aspects, i.e. to question the apparent highly functional multilingualism and analyze its challenges, as well as its positive features. The results are divided into several categories based on how they reflect the various aspects of the dynamics of multilingualism in Luxembourg. These are the demographics and the history of Luxembourg, multilingual education, the presence of EU institutions, the international linguae francae (such as English associated with large international companies and French associated with border workers), the expat environment and minorities and finally, language conflict and discrimination. By analyzing these results and placing them in the corresponding theoretical framework, the thesis offers insight into the complex interplay of various language practices in one of the most multilingual countries in Europe. The results have shown that levels of multilingualism in Luxembourg differ according to social spaces and that impressions of its functioning also vary greatly. The research has exposed significant challenges in the multilingual societal structure, as well as the population’s openness towards social change.