Portugal is one of the oldest countries in Western Europe. By the middle of the thirteenth century the Portuguese kingdom had achieved Portugal’s present borders as well as a degree of internal political, economic, social, and cultural unity that was well ahead of other European monarchies of the time. An oceanic mission had become central to Portugal’s image and definition of its national purpose. Portugal saw itself as a major Atlantic power, as the core of a far-reaching and racially diverse, pan-Lusitanian, global community. Early nation-state development and Portugal’s oceanic policy not only exaggerated the authority and power of the traditional, aristocratically based monarchical system but kept Portugal marginal to the process of industrialization and accompanying social change taking place in northern Europe. The chapter also presents an overview of the key concepts discussed in this book.