The sea is omnipresent in the ancient cultures of the Mediterranean basin. It is an inexhaustible source of food, but also a well-traveled roadway and a means to communicate, trade with, or wage war against one’s neighbors. Perhaps because these practical meanings of the sea were so deeply embedded in daily life, the sea also had a profound religious and symbolic significance for ancient people, from the worship of sea-deities by anxious mariners to the creation of intricate literary devices based on ‘the wine-dark sea’ and concepts such as insularity. People even imagined that, at the edge of the world, where the ocean meets the sky, was the entrance to the Underworld as well as to Olympus, the realm of the gods. In between these distant mythical shores and the well-known contours of the Mediterranean was a space where all utopias and dystopias could be projected—a space to discover and rediscover endlessly. This volume addresses the constant interplay between the real and the imaginary significance of the sea in ancient thought, from philosophy and science to shipbuilding, trade routes, military technology, poetry, mythmaking, and iconography. The volume spans a period of almost two millennia and an area that covers Spain to India and China, and West Africa to the British Isles, demonstrating the global interconnection of cultures and trade, conceived in its broadest possible sense, in the ancient world.