Elwë Sindacollo (shortened in The Silmarillion to Singollo), or Elu Thingol in Sindarin, was one of the three elven ambassadors sent to Valinor by Oromë in the First Age, and King of Doriath. He was the only Sinda to have seen the Two Trees. He had silver hair, and was very tall, and he carried the sword Aranrúth.
He and his brother Olwë led the Teleri to Beleriand, but there he chanced upon Melian. The pair became stricken with love and fell into a trance, and Olwë was forced to lead the those of the Teleri that would follow him to Valinor alone. When Elwë recovered from his trance, he founded the realm of Doriath, and ruled over the remaining Teleri with Melian as his queen. He was known from that point on as Elu Thingol. During the Peace of Arda he hired Dwarves to help build the underground palace of Menegroth, and his only child, Lúthien, was born.
When Morgoth returned to Middle-earth, pursued by the exiles, Thingol enclosed Doriath in the Girdle of Melian, and after hearing of the Kinslaying he refused to have any dealings with the house of Fëanor and banned the use of Quenya in his realm. He later also refused entry to the Edain.
However, Beren found his way through the Girdle of Melian and found Lúthien. When they came to Thingol to ask to be married, Thingol demanded a Silmaril as a bride-price. When, through many trials, Beren succeeded, Thingol was reconciled with the Edain, and Beren and Lúthien were married. Through this kinship, Thingol took in Túrin, and later his mother and sister, Morwen and Nienor. The Silmaril meant that he was drawn into the Doom of the Noldor, though, and Thingol rejected any commands from the sons of Fëanor to return it. Thingol decided to set the jewel into the Nauglamír, a famous necklace of Dwarven make, but the Dwarven workmen killed him, wanting it for themselves. This is probably the cause of the mistrust between Dwarves and Elves.