Giovanni Battista de Rossi (February 23, 1822 – 20 September 1894) was an Italian archaeologist, famous outside his field for his rediscovery of early Christian catacombs.
He was born in Rome. He applied the sciences of archaeology and epigraphy and his thorough knowledge of the topography of Rome and the resources of the Vatican Library, where he was employed cataloguing manuscripts, to Early Christian sites and guided the development of a new field, Christian archeology. He travelled widely, knew all the museum collections intimately and was at the center of a network of professional friendships with all the European scholars of his fields.
In 1849 he rediscovered the lost Catacombs of Callixtus along the Via Appia Antica, with Alexander de Richemont. The catacombs were opened in the early 3rd century, as the principal Christian cemetery in Rome, where nine 3rd-century popes were buried.