Public Diplomacy is that "form of international Political Advocacy in which the civilians of one country use legitimate means to reach out to the civilians of another country in order to gain popular support for negotiations occurring through diplomatic channels."〔Smith Jr., Paul A. ''On Political War'' (Washington: National Defense University Press, 1989).〕

The United States Information Agency, the predecessor to the U.S. State Department’s Undersecretary of State for Public Diplomacy and Public Affairs, defines as public diplomacy as efforts that seek “to promote the national interest of … through understanding, informing and influencing foreign audiences.”

The U.S. State Department’s “Dictionary of International Relations Terms” defines public diplomacy as anything that “refers to government-sponsored programs intended to inform or influence public opinion in other countries; its chief instruments are publications, motion pictures, cultural exchanges, radio and television.”〔

Michael McClellan, one time Public Diplomacy Counselor for the U.S. Embassy Dublin, notes that "public diplomacy () the strategic planning and execution of informational, cultural and educational programming by an advocate country to create a public opinion environment in a target country or countries that will enable target country political leaders to make decisions that are supportive of advocate country's foreign policy objectives."