Public diplomacy is a subfield of political science and international relations that involves study of the process and practice by which nation-states and other international actors engage global publics to serve their interests. It developed during the Cold War as an outgrowth of the rise of mass media and public opinion drivers in foreign policy management. The United States, in a bipolar ideological struggle with the Soviet Union, recognized that gaining public support for policy goals among foreign populations worked better at times through direct engagement than traditional, often closed-door, government-to-government contact. Public diplomacy is still not a defined academic field with an underlying theory, although its proximity to the originator of soft power, Joseph Nye, places it closer to the neoliberal school that emphasizes multilateral pluralistic approaches in international relations. The term is a normative replacement for the more pejorative-laden propaganda, centralizes the role of the civilian in international relations to elevate public engagement above the level of manipulation associated with government or corporate propaganda. Building mutual understanding among the actors involved is the value commonly associated with public diplomacy outcomes of an exchange or cultural nature, along with information activities that prioritize the foreign policy goals and national interests of a particular state. In the mid-20th century, public diplomacy’s emphasis was less scholarly and more practical—to influence foreign opinion in competition with nation-state rivals. In the post-Cold War period, the United States in particular pursued market democracy expansion in the newly industrializing countries of the East. Soft power, the negative and positive attraction that flows from an international actor’s culture and behavior, became the favored term associated with public diplomacy. After 9/11, messaging and making a case for one’s agenda to win the hearts and minds of a Muslim-majority public became predominant against the backdrop of a U.S.-led global war on terrorism and two active interventions in Afghanistan and Iraq. Public diplomacy was utilized in one-way communication campaigns such as the Shared Values Initiative of the U.S. Department of State, which backfired when its target-country audiences rejected the embedded messages as self-serving propaganda. In the 21st century, global civil society and its enemies are on the level of any diplomat or culture minister in matters of public diplomacy. Narrative competition in a digital and networked era is much deeper, broader, and adversarial while the mainstream news media, which formerly set how and what we think about, no longer holds dominance over national and international narratives. Interstate competition has shifted to competition from nonstate actors who use social media as a form of information and influence warfare in international relations. As disparate scholars and practitioners continue to acknowledge public diplomacy approaches, the research agenda will remain case-driven, corporate-centric (with the infusion of public relations), less theoretical, and more global than its Anglo-American roots.