Unicorns are magical horses, white once mature, with a horn protruding from the centre of their foreheads. They are widely considered one of the worst-kept secret of the wizarding world because of how many Muggles are aware of them.

Unicorn foals are born gold in colour until around 2 years old, when they turn silver. Their horn grows in at around 4 years old, and they are considered fully grown at around 7 years, when they are a brilliant white with gold hooves. Mature unicorns preferred to be handled by women, but younger ones are more trusting. Unicorns are not typically aggressive, and are very quick and difficult to catch.

Unicorn hair is used in wandmaking and considered a 'supreme' core. Unicorn hair and horn are also used in potions, including the Antidote to Common Poisons, the Draught of Peace, the Exstimulo Potion, and the Wiggenweld Potion. Unicorn blood can be used to keep someone alive when on the brink of death, but because unicorns are considered pure and sacred, it's said to be a cursed life, as killing one is so heinous.