Andreth (First Age 361 – 455, aged 94 years) was a daughter of Boromir of the House of Bëor and a sister to Bregor. She was called Saelind ("Wise-Heart") by the Elves, for she was wise in thought and learned in the lore of Men. In her youth she dwelt in the house of Belemir, where she had learned the lore of the House of Marach from Adanel.
Andreth was deeply in love with the Elf-lord Aegnor. The love was returned but never fulfilled, since Aegnor felt his coming death, thus they both remained unwed and childless. She had a close friendship with Aegnor's brother, King Finrod Felagund, who often visited her during the Siege of Angband to converse with her on the matters of Elves and Men. One such conversation was written down and later known as Athrabeth Finrod ah Andreth.