This article examines the securitization of delegitimization as a national security threat in Israel. The article contains three elements. First, theoretically, it analyzes legitimacy as a national security asset and delegitimization as a risk to ontological security. Second, it traces the Israeli response to delegitimization, providing an empirically rich account of this approach. Finally, it seeks to provide an assessment, albeit preliminary, of the effectiveness of the Israeli response. It concludes by discussing policy implications, emphasizing the benefits and counterproductive outcomes of an otherwise successful securitization process. Although Israel has had success curbing delegitimization with regard to political elites at the state level, it continues to lose ground with both the grassroots and Western liberal audiences.