In the data-driven economy, personal data has become a strategic asset of firms and a driving engine of market power; accordingly, mergers and acquisitions of companies active in this field carry, beyond their traditional anti-competitive effects, significant consequences for users' privacy. The fundamental question of this research is whether competition law—originally designed to safeguard effective competition and consumer welfare—can and should also protect personal data in the course of these concentrations, and through what mechanisms this protection operates. Employing a descriptive-analytical method within a comparative framework spanning the three systems of the European Union, the United States, and Iran, the article demonstrates that the relationship between these two fields has traversed three stages—"separation," "interaction," and "convergence"—and that today four distinct mechanisms for the competition-based protection of personal data can be identified: quality-based merger review that treats privacy as a non-price parameter of competition, behavioural remedies aimed at prohibiting data combination, control of abuse of a dominant position with respect to unfair data-processing terms, and the obligation to ensure data portability. The findings indicate that the European Union has reached a stage of institutional and substantive convergence, that the United States proceeds cautiously and largely through the concept of quality, and that the Iranian system—owing to the absence of a comprehensive data protection law and the lack of a cooperation mechanism between the Competition Council and the cyberspace regulatory authorities—remains at the stage of separation. The article concludes by proposing the amendment of the merger-related provisions of the Law on the Implementation of the General Policies of Article 44 of the Constitution, the enactment of a comprehensive data protection law, and the design of an institutional cooperation mechanism as the path for the Iranian system's transition to the stage of convergence.