Thranduil
King Thranduil was a character in the fictitious world of Middle-earth created by J. R. R. Tolkien. He was a Sindarin Elf and king of the Silvan Elves in the northern part of Greenwood the Great (Mirkwood), which lay just east of the Misty Mountains.
In The Hobbit he is simply called the Elvenking. When Thorin Oakenshield and his party of Dwarves enter northern Mirkwood they are captured by Thranduil's elves and locked up when they refuse to divulge their intentions, before being freed by Bilbo Baggins. After the death of the dragon Smaug, who had brutalized the Grey Elves for years, Thranduil demanded a share of the treasure the Dwarves recovered from Erebor, Smaug's hideout. Thorin refused, eventually resulting in the Battle of Five Armies.
Thranduil was son of Oropher and father of Legolas Greenleaf. In The Lord of the Rings, the gradually-established friendship between Legolas and the Dwarf Gimli, the son of Glóin of Thorin's band, helps to reconcile Thranduil's people and the Dwarves.
It is amusing to note that one of the dwarves imprisoned by Thranduil was Glóin, Gimli's father, and both Legolas and Gimili most likely grew up hearing tales involving the other's father, yet both end up on a quest together, and develop an unprecedented friendship between Elf and Dwarf.
The appendices to The Return of the King note that Legolas and the Wood-Elves later worked together with Gimli and the Dwarves to rebuild and improve Minas Tirith, capital city of Gondor, the realm of their mutual friend King Elessar.
In the 1977 animated version of The Hobbit, Thranduil is voiced by Otto Preminger.