This article examines Performance Management Systems (PMSs) as socio-technical policy instruments for shaping power relations in megaprojects. Employing an abductive approach, it innovatively applies Foucault's Panopticon theory to the case of the Lyon-Turin railway, a megaproject funded by the European Union's Trans-European Transport Network policy. Our research reveals that PMSs operate as intellectual technologies that enable megaproject promoters to establish control over participants and align their collective behavior with planned policy objectives. We find that this process follows three Foucauldian panoptic principles: hierarchical observation, where participants are organized under nested managerial tiers, establishing vertical lines of command; examination, which uncovers performance flaws; and normalization, which standardizes behavior across the megaproject field. We argue that: PMSs can be employed by policy-makers as instruments to instil governability and shape the collective behavior of megaproject participants consistently with planned policy goals; no matter how effective the panoptic scheme is, there are always avenues of resistance available among those perceiving the megaproject as a threat; and, the configuration and constitution of power relations in megaprojects involve a complex interplay of discipline, sovereignty, and security mechanisms.