The thesis consists in an analysis of the criminal tax frauds between the French, Luxembourg and international tax laws. The comparison of the national French laws and the national Luxembourg laws (First Title) is completed by a part in international law consisting to apprehend the phenomenon of tax fraud within the framework of the international legal assistance in criminal matters, and its potential international limitation in the Grand-Duchy of Luxembourg : the banking secrecy (Second Title).After having analysed the applicable national laws, the First Title of the thesis deals with the question of the criminal procedure applicable for criminal tax evasion and tax fraud before the criminal French and Luxembourg Courts.Due to the globalisation of the capital flows, criminal behaviour of tax payers became more and more complex, structured, and, in certain particular cases, organized as real factories of international tax fraud. The Second Title of the thesis is consequently dedicated to the analysis of international tax fraud and international legal assistance in criminal matters in the area of tax frauds. This second parts deals also with, within the scope of a French-Luxemburgish comparison, of the Luxembourg banking secrecy. ; La thèse consiste en une mise en perspective des délits pénaux fiscaux en droits français, luxembourgeois et internationaux. La comparaison des droits nationaux français et luxembourgeois (Titre Premier) est complétée d'un volet en droit international qui consiste à appréhender le phénomène de la fraude fiscale sous l'angle de l'entraide judiciaire internationale, et de son éventuelle limite internationale au Luxembourg : le secret bancaire (Titre Deuxième).Après avoir procédé à l'analyse des droits positifs nationaux, le Titre Premier de l'étude aborde la question de la procédure pénale applicable pour fraude fiscale et escroquerie fiscale devant les juridictions nationales, ainsi que les peines encourues devant les juridictions répressives françaises et luxembourgeoises en la ...