Liz Halliday (born 1971) is a British author who writes under the name Mags L Halliday in Doctor Who-series of science fiction. She is distinct from the writer Liz Holliday, who has also contributed to Doctor Who-related science fiction.
Her published work includes the Doctor Who novel History 101 (2002) and contributions to the Faction Paradox series including the novel Warring States (2005).
Halliday contributed material to the Faction Paradox anthology/encyclopedia The Book of the War (2002) about a Russian Soviet splinter group from the Faction whose members include Anastasia Romanova and Rasputin. Her Faction Paradox novel, Warring States focuses on an English Faction agent and a young Chinese woman who come into conflict during the Boxer Rebellion.