Locusta or Lucusta (died 69), was a notorious maker of poisons in the 1st-century Roman Empire, active in the final two reigns of the Julio-Claudian dynasty. She supposedly took part in the assassinations of Claudius and Britannicus. She was a favourite of emperor Nero for several years, and Nero had her provide training to other poisoners in his service. Following Nero's death, Locusta was executed by his successor, Galba (reigned 68–69).