Aqua Tofana (Ital. acqua della, Toffanina), a secret poison employed in Italy during the latter part of the 17th century, and said to have been invented by a woman named Tofana, a native of Sicily, who lived for a time in Palermo, and subsequently in Naples, where she exercised her criminal art on a large scale. Her customers are said to have been chiefly young wives who wished to be rid of their husbands; and when the number of mysterious deaths about the year 1059 at last aroused suspicion, a secret society of young married women was discovered, presided over by a creature called La Spara, who had learned the art of poisoning from Tofana. La Spara and several others were executed. Tofana was thrown into prison, but the date and manner of her death are uncertain. According to Labat, a French traveller, about 1709 she was seized in a convent in which she had taken refuge, and having, on being tortured, confessed 000 poisonings, she was strangled in prison. On the other hand, Keysler, a German traveller, says he saw her in prison at Naples, a little old woman, in 1730. The poison was put up in small phials, labelled " Manna of St. Nicholas of Bari," with an image of the saint on one side.

Incredible and contradictory accounts are given of its nature and effects; it is most probable that it was essentially a strong watery solution of arsenic obtained by long boiling. The use of such an article, even in the dose of five or six drops, frequently repeated for a length of time, would cause death with many of the symptoms ascribed to the aqua Tofana.