This article traces the history of Amélie de Dietrich in her role (1806 to 1855) as the head of one of the oldest family-owned businesses in Europe: the De Dietrich Company. Economic history has long given a very minor place to women entrepreneurs. Recent analyses nevertheless tend to show that women business leaders were not exceptions in the nineteenth century. This paper is a further attempt to bring women entrepreneurs – and their contribution to the industrial take-off – out of invisibility. Amélie de Dietrich took important strategic decisions to adapt the company to the new economic opportunities which arose in the first half of the nineteenth century. Her choices were decisive for the future of the company; what is more, she succeeded in restoring the familial ownership. Drawing on Amélie de Dietrich’s own unpublished correspondence, this contribution examines the factors that explain her success in imposing herself as a Maître des Forges.