Annie Elizabeth Fredericka Horniman (3 October 1860 – 6 August 1937) was an English theatre patron manager and occultist. She was a member of the Assassin Order and later on the Hermetic Order of the Golden Dawn.
From 1882, Annie Horniman visited the Slade School of Fine Art, where she met and befriended Mina Bergson, later known as Moina Mathers. Annie introduced her new friend to the Brotherhood of Assassins. Moina never developed a strong religious faith and since the Brotherhood sought protecting free thoughts by any means, she welcomed the group's free spirit.
In 1890, Annie became a member of the Hermetic Order of the Golden Dawn which was founded by Moina's husband, Samuel Liddell Mathers. About six years later, Annie began to disagree with certain aspects of the order which she considered as immoral which eventually led to her resignation in 1903, shortly before the fall of the order.
- In 2015, her name was on a list of known British Assassins used by the Templar Isabelle Ardant.