The god associated with agriculture and grain in both Greek and Roman mythology is Demeter in Greek mythology and Ceres in Roman mythology. Both deities symbolize fertility, the harvest, and the nurturing aspects of nature. Demeter/Ceres is intricately linked to the changing seasons, particularly the cycle of planting and harvest linked to the myth of her daughter, Persephone. Their worship underscores the importance of agriculture in ancient societies, illustrating how seasonal changes affected life and culture, emphasizing the vital connection between humanity and the earth.