Countess Elizabeth Báthory (Báthory Erzsébet in Hungarian, Alžbeta Bátoriová in Slovak, Alžběta Báthoryová in Czech, Elżbieta Batory in Polish, 7 August 1560 – 21 August 1614) was a Hungariancountess from the renowned Báthory family. The family is famous for defending Hungary against theOttoman Turks. She is possibly the most prolific female serial killer in history and is remembered as the "Blood Countess" and as the "Bloody Lady of Csejte", after the castle near Trencsén (Trenčín), in the Kingdom of Hungary (present Slovakia), where she spent most of her adult life.

After her husband's death, she and four collaborators were accused of torturing and killing hundreds of virgin girls and young women, with one witness attributing to them over 600 victims, though she was only convicted on 80 counts. In 1610, she was imprisoned in Csejte Castle (Čachtice Castle), where she remained bricked in a set of rooms until her death four years later. She was never formally tried in court.

The case has led to legendary, but false, accounts of the Countess bathing in the blood of virgins in order to retain her youth. These stories have led to comparisons with Vlad III the Impaler of Wallachia, on whom the fictional Count Dracula is partly based, and to modern nicknames of the Blood Countessand Countess Dracula.