Samuel Liddell (or Liddel) MacGregor Mathers (January 8 or 11, 1854 – 5 or 20 November 1918), born Samuel Liddell Mathers, is a British occultist.
He is primarily known as one of the founders of the Hermetic Order of the Golden Dawn, a ceremonial magic order of which offshoots still exist.
He becomes so synonymous with the order that Golden Dawn scholar Israel Regardie will observe in retrospect that "the Golden Dawn was MacGregor Mathers."