Lizzie Halliday (born Eliza Margaret McNally; c. 1859 – June 28, 1918) was an Irish-American serial killer responsible for the deaths of four people in upstate New York during the 1890s.

[2][3] In 1879, Halliday married a Greenwich, New York, man known by the alias Charles Hopkins; his real name was Ketspool Brown.

After a reported failed attempt to kill Smith by putting arsenic in his tea, Lizzie fled to Bellows Falls, Vermont.

[3] In the winter of 1888, Halliday resurfaced in Philadelphia, at a saloon on 1218 North Front Street that was run by the McQuillans, friends she knew from Ireland.

In 1889, now going by the name "Lizzie Brown", she became the housekeeper for Paul Halliday, a twice-widowed 70-year-old farmer living in Burlingham, New York, with his sons.

She claimed that he died trying to save her from the flames, but his locked bedroom door was discovered in the rubble, and Halliday was in possession of the key.

Following the neighbors' suspicions that something was not right about her story, a search warrant was obtained, and on September 4 the bodies of two women were found buried in hay in a barn.

The women were later identified as Margaret and Sarah McQuillan, New York residents who were part of the family Lizzie had stayed with in Philadelphia.

While she was in jail, Lizzie received national attention, with one sensational story after another appearing across the country in tabloid newspapers.

[3] Lizzie also made a claim (confided to Robert Halliday) that she had killed a husband in Belfast,[7] but had managed to conceal the crime.

Governor Roswell P. Flower commuted her sentence to life in a mental institution after a medical commission declared her insane.