Who was the first serial killer in the world?

Serial murder is not new, predating accurate written records. One of the earliest on record was French nobleman Gilles de Rais, who in the years between 1435 and 1440 sodomized and murdered hundreds of young boys at his estate in Machecoul, Pays de Retz, France. The charges read, murder of children and sodomy, the invocation of demons, the offering of Devine Majesty and heresy. He was found guilty and hanged on October 26, 1440, at Nantes.

Romainian Countess Erszebet Bathory killed an estimated 600 young girls at her castle near Trencin, Hungary, from 1602 to 1610. Finally arrested in 1611, she was banished to the tower in her own castle where she died on August 21, 1614.