Patchouli Knowledge (パチュリー・ノーレッジ Pachurii Noorejji) is a witch and resident of the Scarlet Devil Mansion in the library. She's friends with the mistress of the house, Remilia Scarlet, and acts as resident librarian. She's known as a highly capable, experienced, and studious magician, usually found researching the countless tomes within the house library. But her great abilities are offset by her poor health, caused by long-time reclusivity and asthma.

Her hair and eyes are purple, and has many ribbons tied to her hair and other parts of her clothing. She wears pink pajama-like clothing and a night-cap with a gold crescent moon on it. Her dress in some appearances looks like it has stripes of purple and violet.

Ability: Manipulation of fire, water, wood, metal, earth, sun, and moon.