Erendis was a woman of Númenor and was of the House of Bëor through ancient lines of descent.

She it was who wed Tar-Aldarion who became the sixth of the Kings of Númenor. She bore to him a daughter who was called Tar-Ancalimë.

Tar-Aldarion's great love was the sea and he spent long years sailing far and wide, but Erendis had no love of the water and she remained instead on Númenor awaiting Aldarion's return.

The love between Erendis and Tar-Aldarion eventually turned to hate and they became estranged and separated in SA 882. Erendis also became estranged from her daughter, Tar-Ancalimë, and she finally "perished in water in the year 985." (Unfinished Tales, Aldarion and Erendis)
Encyclopedia entry originally written by Nienna-of-the-Valar