The great bay to the south of Beleriand into which the River Sirion flowed.

Before the First Age and after the Battle of the Powers, the great sea that separated Middle-earth from Aman grew wide and deep. It made a deep gulf to the south, and many lesser bays were made between the Great Gulf and Helcaraxë far in the north, where Middle-earth and Aman came together. Of these the Bay of Balar was the chief and the largest.

To its north was the land of Arvernien where the Exiles of Gondolin dwelt and from where Eärendil set out on his voyage to Aman. To the east was the unsettled forest of Taur-im-Duinath.

In the Bay of Balar, Ulmo anchored Tol Eressëa. When the Vanyar and the Noldor embarked upon the isle and were drawn over the sea, the eastern horn of the isle was broken off and remained behind, and was called the Isle of Balar.

After the War of Wrath, the world was again changed and the Bay of Balar was destroyed along with the rest of Beleriand.
Encyclopedia entry originally written by Ellethiel