Fawkes is Albus Dumbledore's pet phoenix. Phoenix tail feathers are suitable for inclusion in some wands; Fawkes himself provides the feathers for both Harry's and Voldemort's wands. Because of this, in the series "Harry Potter and the Goblet of Fire," during the duel between Harry and Voldemort, The "reverse spell effect" occurred (known as 'Priori Incantatem'), as both of their wands were made of Fawkes feather. A sweet song of hers is heard by Harry when the two wands come in contact, the wands seal off the duel from outside interference, and one of the wands, in this case Harry's, makes Voldemort's wand regurgitate its last spells one by one by producing some sort of cloudy echo of the objects conjured and people killed by the wand. Whenever Fawkes dies, whether by violence or of old age, he bursts into flame and is promptly reborn out of the ashes as a baby phoenix with the appearance of a newborn chicken and in his geriatric stages he has dull, limp plumage like a "half-plucked turkey." However, as an adult, he is about swan-sized and possesses magnificent red and gold plumage.

In Harry Potter and the Chamber of Secrets, Fawkes is summoned by Harry's loyalty to Dumbledore to the aid of the protagonist as the boy fights against Salazar Slytherin's basilisk. Fawkes gouges the basilisk's eyes out, blinding it and eliminating its ability to kill with its gaze. Harry is later wounded by the basilisk's fang; he nearly dies from the venom, but Fawkes heals the wound with his tears, as phoenix tears have healing powers and are the only antidote for basilisk venom. Fawkes then brings Harry, Ron, Ginny, and Gilderoy Lockhart back up to the castle, bearing their combined weight as they hold his tail feathers. Fawkes also has the ability to teleport himself and others in a burst of flame. During the confrontation between Voldemort and Dumbledore in the Ministry in the climax of Harry Potter and the Order of the Phoenix, Fawkes saves Dumbledore's life by swallowing a Killing Curse from Voldemort. Fawkes then bursts into flame and is reborn as a chick from the ashes. After Dumbledore's death in Harry Potter and the Half-Blood Prince, Fawkes is heard singing a lament for him. When the singing stops, Harry knows that Fawkes has left Hogwarts forever.

According to Rowling, Fawkes is named after 17th century conspirator Guy Fawkes.