The Python still takes the title of the world’s longest snake, but in terms of diameter and weight, the anaconda is not only the largest in South America and the Amazon rainforest but also the world. The Green Anaconda, or Eunectes murinus, is the heaviest, largest, and longest snake in South America. Many legends and lore circulate around the length of the Giant Anaconda. Green Anaconda (Eunectes murinus) seen in the Cuyabeno Wildlife Reserve 2.