Although history ultimately favored the portuary development of Sài Gòn and Hải Phòng, it was Tourane (Đà Nẵng) that was the initial target of French colonial ambitions in the Indochinese peninsula. For over a century (1740-1858), its bay and territory had been the scene and the epicenter of Franco-British overseas imperial rivalries, a fact which actively fostered an entire set of colonial images about the site, which was quite often referred to as potential base to serve the interests of commerce and the Navy. Despite these ambitions nurtured over a long period, it was only after the conquest of Tonkin, thirty years after the Cochinchina expedition, that its territory was finally established as a concession: on 3 October 1888, the French were finally seizing juridical control of Tourane. As a conceded territory, Tourane was essential to French colonial and imperial designs. The focal point of political and economic ambitions, it was both a gateway and a means to prepare and support the French colonial project in Indochina. A hybrid and previously unknown template, the conceded territory model designed for, and from, Tourane indeed allowed the French to implement new strategies to tighten colonial rule in Indochina. Offering an unprecedented analysis on the creation of the French concession of Tourane at the end of the 19th century, this research examines the political context during which it was conceived, the work and conclusions given by the commission in charge of studying its borders and jurisdiction, and the steps taken by the colonial administration in order to seize definitive control of a strategic territory inside what was then left of the Đại Nam Kingdom. All in all, comparing Tourane with others treaty ports, it shows how and why its territory stood out as a micro-colony in a protectorate territory (Annam-Tonkin).