Which Tolkien character is the father of Legolas?

Thranduil is the father of Legolas in Tolkien’s legendarium.

Thranduil is the Elvenking who rules the Woodland Realm in northern Mirkwood. He appears directly in The Hobbit, where his kingdom becomes involved in the events surrounding the Dwarves, Lake-town, and the Battle of the Five Armies. Legolas is identified in The Lord of the Rings as Thranduil’s son and represents the Woodland Realm in the Fellowship.

Oropher, not Thranduil, is Thranduil’s father and Legolas’s grandfather. Oropher was a king of the Silvan Elves and died during the War of the Last Alliance. Tolkien gives relatively little biographical detail about Legolas, so later adaptations and expanded materials sometimes encourage confusion about his family history.