In Hindu mythology, the demon king defeated by Rama is Ravana. As the ruler of Lanka, Ravana had immense powers and was known for his knowledge and strength. His kidnapping of Rama's wife, Sita, led to the epic conflict depicted in the Ramayana. Rama, with the help of allies like Hanuman and the monkey army, fought a fierce battle against Ravana. Ultimately, Rama's triumph over Ravana symbolizes the victory of good over evil and remains a vital narrative in Indian culture and tradition.