The mythical hero credited with founding the city of Thebes in Greek mythology is Cadmus. He is renowned for his adventurous journey to seek his sister, Europa, and his subsequent establishment of Thebes. Cadmus is also known for introducing the alphabet to the Greeks, signifying his connection to knowledge and civilization. His story intertwines themes of fate, loss, and the founding of cities, underscoring the importance of mythological narratives in explaining the origins of places and cultural practices.