This article deals with the world of French State engineers in the first half of the 19th century and it aims to present an overall perspective of its most marked features. After briefly examining the different engineering corps of the Ancien Régime and their training institutes, it goes on to deal with the foundation of the Ecole Polytechnique in 1794, which gave French State engineers a unity and a collective identity that had heretofore been lacking, and transformed them into members of a technocratic milieu. The core of the article consists of exploring the professional aspects of this 'technocracy' (its internal organization, the values and self‐image of its members, etc.), its cultural and intellectual features, especially the idea of systematically 'applying' scientific knowledge to the practical problems encountered by engineers, and the profile of the technocratic intellectual elite, i.e. the engineer‐savant, the proponent and 'implementer' of the 'application' ideal.