Phoenix feathers are feathers shed by phoenixes, primarily gathered and used in wandmaking.
This is the rarest core type. Phoenix feathers are capable of the greatest range of magic, though they may take longer than either unicorn hair or dragon heartstring cores to reveal this. They show the most initiative, sometimes acting of their own accord, a quality that many witches and wizards dislike.
Phoenix feather wands are always the pickiest when it comes to potential owners, for the creature from which they are taken is one of the most independent and detached in the world. These wands are the hardest to tame and to personalise, and their allegiance is usually hard won.
Harry Potter's and Tom Riddle's wand cores came from the same phoenix: Fawkes, who belonged to Albus Dumbledore; these two wands are brothers. Therefore, they have a certain connection and may produce unusual magical effects when forced to duel one another, a phenomenon known as Priori Incantatem. Riddle, better known as Voldemort, kidnapped Ollivander, the wand maker, for information on this situation and how to overcome it. Ollivander told him that a different wand may work against Harry, but Harry's wand destroyed the "borrowed" wand when Lord Voldemort chased him when Harry was being moved.
The only phoenix known to have donated his feathers to make a wand was Fawkes, Albus Dumbledore's magical bird. He only gave two feathers, one to Harry Potter's wand, and one to Tom Riddle's wand. 
There was at least one other phoenix who donated its feather to Ollivander as shown in the maple wand Ollivander showed Harry in 1991. Who this phoenix was and how its feather was attained is unknown.
Behind the scenes
- Harry Potter series author J. K. Rowling, if given the choice, would the core of her own wand to be a phoenix feather, which was the reason why she gave Harry this core.
- Harry Potter and the Philosopher's Stone (First mentioned)
- Harry Potter and the Philosopher's Stone (film) (Mentioned only)
- Harry Potter and the Chamber of Secrets (Seen on phoenix) (Possibly)
- Harry Potter and the Chamber of Secrets (film) (Seen on phoenix)
- Harry Potter and the Chamber of Secrets (video game) (Seen on phoenix)
- Harry Potter and the Goblet of Fire (Mentioned only)
- Harry Potter and the Order of the Phoenix (Warning sign) (Possibly seen on phoenix)
- Harry Potter and the Order of the Phoenix (film) (Seen on phoenix)
- Harry Potter and the Half-Blood Prince (Possibly seen on phoenix)
- Harry Potter and the Half-Blood Prince (film) (Seen on phoenix)
- Harry Potter and the Deathly Hallows
- Harry Potter and the Deathly Hallows: Part 1