The wide bay in the western part of Númenor, between the promontories of Andustar to the north and Hyarnustar to the south. It was fed by the River Nunduinë, and its mouth was more than a hundred miles across, making it by far the largest bay in the shores of Númenor.

From Númenor's earliest days, the bay was associated with the Eldar of Tol Eressëa, who dwelt west of Númenor in the Undying Lands. The port of Eldalondë - 'Elf Haven' - stood at the mouth of Nunduinë where it emptied into the bay, and the name Eldanna itself means 'towards the Eldar'.