His name in Quenya was Artaresto. Orodreth was born in Valinor to Angrod and Eldalôtë, a Noldorin lady whose name in Sindarin became Edhellos. Together with Turgon's daughter Idril and Curufin's son Celebrimbor, he was one of the three members of the Noldorin royal family in the third generation to come into exile. While He and his father held Dorthonion, his son, Gil-galad, was sent to the more safe Nargothrond with his granduncle Finrod.
Orodreth held the tower of Minas Tirith on the island of Tol Sirion in the vale of Sirion until Sauron overran the isle and renamed it Tol-in-Gaurhoth. Orodreth then fled south to Nargothrond. Without the aid of Celegorm, and Curufin, who had suddenly attacked the forces of Sauron with whatever forces they could gather, Orodreth might have fallen.
When Beren came to Nargothrond, Finrod went with him on his quest for the Silmaril. However Celegorm and Curufin the Sons of Fëanor were also at Nargothrond, and forced Finrod to lay down his crown. Orodreth took it, ruling as regent, but the Sons of Fëanor held the real power.
When news came that Finrod had been killed, the Sons of Fëanor were expelled from Nargothrond, and Orodreth became its leader.
When Túrin Turambar arrived in Nargothrond he gradually became its de facto leader, although Orodreth remained lord in name.
In earlier versions of the Silmarillion legendarium as detailed in the History of Middle-earth series, Orodreth was a more important character, and the original king of Nargothrond. However, his importance diminished over time. In the published version of The Silmarillion, he was the second son of Finarfin, with Finrod, Angrod, Aegnor, and Galadriel being his siblings. He succeeded Finrod as the king of Nargothrond and had only one child, Finduilas (Gil-galad was the son of Orodreth's cousin Fingon). Orodreth was killed at the forefront of the Battle of Tumhalad and Finduilas was taken and slain shortly afterwards. The only other member of the house of Finarfin to have descendants was Orodreth's sister Galadriel, who had left Beleriand before the end of the First Age.
In the published Silmarillion, Orodreth is a son of Finarfin, with Quenya name Artanáro. This was an editorial decision by Christopher Tolkien, made on the grounds that the later revision was not fully integrated into the extant texts by his father. Gil-galad, later High King of the Noldor, was his son (in the latest writings by Tolkien), but in the published Silmarillion Gil-galad is made into Fingon's son instead. Unlike in the matter of Gil-galad, Christopher Tolkien believed that the decision to make Orodreth the son of Angrod was final. An earlier idea was that Orodreth's son was named Hallas, but Gil-galad replaced him.
In his last writings, Tolkien changed Orodreth's name to Artaher (Quenya) / Arothir (Sindarin), but it was never introduced in any narratives, so Christopher Tolkien left the name Orodreth unchanged. It is probable that the Sindarin name Orodreth would have been retained nonetheless: Tolkien seldom changed names after they had long been used, even if only in unpublished writings.