The Guild of Venturers was formed in Númenor by Prince Anardil (later known as King Tar-Aldarion, the Great Captain). The guild was formed by Anardil for the purpose of exploring Middle-earth. Its guildhouse was located aboard Anardil's great ship Eämbar, which was moored on the small island of Tol Uinen, which was named after the sea Maia, Uinen. Tol Uinen was located in the Bay of Rómenna.
In Númenor, the guild was called the Uinendili. Uinendili meant "Lovers of Uinen". The members of the guild were strong devotees of Uinen, the Lady of the Seas, whom they believed favored their journeys. Members of the guild were considered the most adventurous men of Númenor. The guild made journeys across Middle-earth. They would travel from the Northern Darkness to the far south all the way down to the Nether Darkness. They traveled the inland seas of the east towards the Walls of the Sun, which was as far as they would dare to venture. The only land the guild did not travel to was the Undying Lands of Valinor, which they were not permitted to enter. The Guild of Venturers gave the Númenóreans the title of Kings of the Sea.