“Coopetition” is a phenomenon, generally studied in market economy (Nalebuff & Brandenburger, 1996), which establishes the necessity to unify opposing forces to confront a common threat or to gain a collective competitive advantage. Thus “coopetition” is derived from strategy of a network where it is neither about attaining a critical size nor of competing to eliminate its adversaries. It is, rather, a question of collaboration with the competition to protect the common good from destructive channels of activity, whether from a profession or from a technology. This article presents the concept of “coopetition” in the sphere of public territorial management as inspired by the theoretical works by Bengtsson and Kock (1999; 2000). The research question is to understand what extent collaboration in competition is a generalized practice, not only in the sphere of market economy, but equally in the management of local government. Relying on the study of an exploratory case devoted to the cooperation of 169 communes in the Rhone Alps, completed by an investigative team of nearly 250 territorial directors, the main results of the research are the following ones: within the limits of the field of investigation, the observations of public management regarding “coopetition” processes validate the current theory of private management. More precisely, “coopetition” among local authorities proves advantageous for protecting the common good, the well-being, of a territory, by zeroing in on initially non-compatible objectives among the territorial strata. The conditions for such outcomes rely on equality of principals in governance and avoidance of conflicts of interest in management teams.