Jacob Black is a shape-shifter or "werewolf" of the Quileute tribe, former Beta of the Uley pack, and Alpha of his own. In Twilight, he is fifteen years old, and in New Moon, he phases into a wolf for the first time at the age of sixteen. In Breaking Dawn, he imprints on the hybrid baby named Renesmee Cullen, the daughter of Edward Cullen and Bella Swan.

On Stephenie Meyer's official website, Jacob was originally just a device to inform Bella about the "Cold Ones." However, both she and her editor liked Jacob so much that they decided to give him a larger role in the sequels to Twilight, making him a main character in New Moon, Eclipse, and Breaking Dawn. He forms a deep bond with Bella in the sequels, and tries to fight against Edward for her love , until she realizes that her love for Edward is stronger and chooses him over Jacob. Jacob subsequently imprints on Bella and Edward's daughter, Renesmee, thus freeing himself from his heartbreak and triangular issues with Bella and Edward.