Nowadays there are two main interpretations of the concept of "ecoterrorism". According to the first interpretation, environmental organizations are classified as ecoterrorist organizations that fight for animal rights and against pollution using violent methods of a criminal nature. In conformity with the second interpretation, the concept of ecoterrorism is interpreted more broadly and includes acts of deliberate damage to the environment to achieve certain political and other goals. After conducting a comparative political and legal analysis of ecoterrorist organizations in different countries (primarily, the United States and Russia) and their activities in national legislations, the authors of the article have concluded that the absence of a single and internationally recognized definition of ecoterrorism is associated with the ideological assessment of the phenomenon of "terrorism", on the one hand, and with the clash of not only different concepts but also various methodologies typical of the political and legal field of a given country, on the other hand. Due to various interpretations of environmental terrorism, a list of generally recognized international ecoterrorist organizations has not been compiled, which hinders any counteraction to ecoterrorism.