In recent decades, the progress in archaeology applied to knowledge of the Roman cities in the Catalan-speaking lands has begun to furnish a new perspective on the question of the origins of these cities. In this article, which focuses on Catalonia, and in the one planned for the next issue focusing on Valencia, we shall examine this topic, which also provides valuable information on the Romans’ earliest presence here. With just a handful of exceptions, the majority of Roman cities documented in Catalonia were newly founded by the Romans. With them, a network of new cities was built that had a profound influence on the process of Romanisation that had gotten underway during the Second Punic War and culminated at the end of the Republican period with the founding of Barcino, the predecessor of today’s Barcelona. The archaeological information provided by the cities of Tarraco, Baetulo, Iluro, Iesso, Aeso, Gerunda and Roman Emporiae, among others, furnishes fragmentary yet highly significant information that enables us to fine-tune the chronologies of their starting dates and the characteristics of their earliest development with regard to the historical context of the time, which unquestionably marked the first steps in their formation as cities. The early years of the 1st century AD were particularly dynamic in terms of this urbanising activity, which was most likely not just inspired but also planned by the Roman authorities. The new cities, with their regular layouts in rigorously orthogonal grids and their fortified premises, brought to Catalonia the urban models that the Romans had developed during their years of expansion around the Italian peninsula. Along with the construction of the roadway network, they would lay the foundations for the structure of the country, which would mark the entire Roman period and largely remain in place in the subsequent centuries and even until today.