Beren was the son of Barahir, a Man of the royal House of Bëor of Dorthonion, and the most accomplished hero and adventurer of the First Age. The battle of the Dagor Bragollach befell during his youth, bringing about the ruin of his kingdom. The young Beren lived with his father and ten loyal followers in the highlands of Dorthonion, and the twelve of them performed many acts of bravery, to the great frustration of Morgoth. After the ruin of the Outlaws of Dorthonion, Beren left the land of his birth. He crossed into Doriath, where he saw and fell in love with Lúthien, princess of the Sindar and daughter of Thingol and Melian.
Thingol haughtily refused to give Lúthien's hand in marriage. He said that he would allow the marriage to take place if Beren brought back a Silmaril from the Iron Crown of Morgoth. Nobody believed that the task could be done, but Beren and Lúthien braved many impossible perils and captured the Silmaril. However, as they escaped from Angband, the great guard-dog Carcharoth, whom Morgoth had personally bred, awoke. Beren held out the Silmaril, hoping that its radiance would avert the beast, but he was mistaken. Carcharoth bit off his hand swallowed it and the Silmaril, and proceeded to run rampant through Doriath. Lúthien and the unconscious Beren were rescued by the Eagles of Manwë. Beren lived to participate in the Hunting of Carcharoth, where the beast was slain and the Silmaril recovered, but he was mortally wounded there.
Lúthien's love for Beren was so strong that, hearing of his death, she laid down and died - or at least appeared to die. Her soul went to the Halls of Mandos, where all dead Elves go. She had been the world's greatest singer, and even after her death, she managed to charm Mandos into granting her a wish. Both she and Beren were restored to life, but with their souls were tied together. Both of them would die the death of Men, and go beyond the walls of Arda to a place unknown. Thus Beren and Lúthien lived again, and dwelt on Tol Galen in the middle of the river Adurant in Ossiriand. Lúthien bore Beren a son, named Dior, Thingol's heir, considered to be one of the fairest beings to ever live, for in him flowed the blood of Men, the blood of Elves, and the blood of the Ainur.