This report examines Russia's growing use of private military companies (PMCs) to increase its influence through irregular means. In recent years, Moscow has expanded its overseas use of PMCs to countries such as Ukraine, Syria, Libya, Sudan, the Central African Republic, Madagascar, and Mozambique. Many of the PMCs operating in these countries, such as the Wagner Group, frequently cooperate with the Russian government--including the Kremlin, Ministry of Defense (particularly the Main Intelligence Directorate, or GRU), Foreign Intelligence Service (SVR), and Federal Security Service (FSB)--and perform a variety of combat, paramilitary, security, and intelligence tasks. However, many of these PMCs have a poor track record--including operational failures and human rights abuses--and there are opportunities to exploit PMC vulnerabilities. Although Russian PMCs present only one of a variety of national security threats and challenges facing the United States, this report assesses that they warrant a more substantive and coordinated response from the United States and its partners.