Marguerite Frieda Harris, Lady Harris, referred to, by her own insistence, as Lady Frieda Harris, was an English artist and, in later life, an associate of the occultist Aleister Crowley. She is best known for her design of Crowley's Thoth tarot deck.

Thoth Tarot is an esoteric tarot deck painted by Lady Frieda Harris according to instructions from Aleister Crowley. Crowley referred to this deck as The Book of Thoth, and also wrote a 1944 book of that title intended for use with the deck.