The ancient civilization that believed in the god Quetzalcoatl is the Aztecs. Quetzalcoatl, the Feathered Serpent, was a major deity symbolizing life, knowledge, and wind. Revered as a creator god, he played a crucial role in the Aztec cosmogony and was associated with fertility, learning, and the agriculture that sustained their society. His influence extended to various aspects of culture, including art and religion.