Giovanni Battista Agnello (fl. 1560–1577) was a Venetian alchemist working in London in the 1560s and 1570s. He was the author of the second book in Italian printed in England, Espositione sopra vn libro intitolato Apocalypsis spiritus secreti.[1] He was also the first to declare that the ore brought back by Martin Frobisher from Baffin Island contained gold.