Lammas Night is a fantasy novel by the American-born author Katherine Kurtz, first published in paperback by Ballantine Books in December 1983.

Lammas Night tells the story of a group of English witches who act to save their country from Nazi attack during the Second World War.

Woven within the story of their efforts are the visions and fragmented memories of a male witch, who gradually comes to realize his role in an ancient cycle of royal death, reincarnation, and sacrifice.

While Gray uses Jordan's collected information to plan a more conventional psychological warfare campaign against the Nazi invasion, he also attempts to unify the many disparate groups of British occultists to work in concert on Lammas night, one of the major Sabbats.

The Prince eventually volunteers to be the royal patron of the Oakwood Group and its Lammas night undertaking, but as Gray Graham works to develop his network of occultists the Battle of Britain reaches its crescendo.