The paper examines public debt from the viewpoint of national security and sovereignty. The current situation with public debts in different types of countries is revealed. The risks, challenges and threats in the public debt sphere are presented. Different forms of public borrowings, such as loans from international organizations and banks, issuance of the securities on the domestic and international markets were analyzed. It was shown, that the international credits are characterized by the conditionality. In the case of borrowing on the open market using securities, the debtor depends on the current market conditions and can face significant deterioration of the situation. It was proved, that no form of borrowing is free from potential problems. The suggested classification of risks, challenges and threats can be useful for the efficiency of the public debt management.