Decades of the New World (Latin: De orbe novo decades; Spanish: Décadas del nuevo mundo), by Peter Martyr d'Anghiera, is a collection of eight narrative tracts recounting early Spanish exploration, conquest and colonization of the New World, exploration of the Pacific, and related miscellany. The first four of these tracts were first published disjointly in three volumes in 1511, 1516, and 1521. All eight tracts were first anthologized, that is, first published as the completed Decades of the New World collection, in 1530. Being among the earliest histories of the Age of Discovery, the Decades are of great value to the history of geography and discovery.

In 1530 the eight Decades were published together for the first time at Alcalá. Later editions of single or of all the Decades appeared at Basel (1533), Cologne (1574), Paris (1587), and Madrid (1892). A German translation was published in Basle in 1582; a French one by Gaffarel in Recueil de voyages et de documents pour servir à l'histoire de la Geographie (Paris, 1907).

The first three decades were translated into English by Richard Eden and published in 1555 (found in Arber's The first three English books on America Birmingham, 1885), thus beginning the genre of English discovery travel writing, which stimulated English exploration of the New World.^[1] Eden's translations were reprinted with supplementary materials in 1577 by Richard Willes under the new title, The historie of travayle into the West and east Indies. Richard Hakluyt had the remaining five decades translated into English by Michael Lok and published in London in 1612.

The Decades describe the early contacts of Europeans and Native Americans derived from narratives of the voyages of Christopher Columbus in the Caribbean, reports from Hernán Cortés's Mexican expedition, and other such resources. They consisted of eight reports, two of which Martyr had previously sent as letters describing the voyages of Columbus, to Cardinal Ascanius Sforza in 1493 and 1494. In 1501 Martyr, as requested by the Cardinal of Aragon, added eight chapters on the voyage of Columbus and the exploits of Martin Alonzo Pinzón. In 1511 he added a supplement giving an account of events from 1501 to 1511. By 1516 he had finished two other Decades:

• The first was devoted to the exploits of Alonso de Ojeda, Diego de Nicuesa, and Vasco Núñez de Balboa. It was first published against his consent in a Venetian-Italian summary in Venice in 1504, reprinted in 1507, and published in a Latin translation in 1508. The original Latin text was published in 1511.^[2]
• The second gave an account of Balboa's discovery of the Pacific Ocean, Columbus' fourth voyage, and the expeditions of Pedrarias Dávila.
• The first three appeared together at Alcalá de Henares in 1516 under the title: De orbe novo decades cum Legatione Babylonica.
• The Enchiridion de nuper sub D. Carolo repertis insulis (Basle, 1521) was printed as the fourth Decade, describing the voyages of Francisco Hernández de Córdoba, Juan de Grijalva, and Hernán Cortés.
• The fifth Decade (1523) dealt with the conquest of the Aztec Empire and the circumnavigation of the world by Ferdinand Magellan.
• The sixth Decade (1524) gave an account of Dávila's discoveries on the west coast of America.
• The seventh Decade (1525) had collected descriptions of the customs of the natives in present-day South Carolina, including the "Testimony of Francisco de Chicora", a Native American taken captive there; as well as those of natives in Florida, Haiti, Cuba, and Darién.
• The eighth Decade (1525) told the story of the march of Cortés against Olit.

• P. Martyris ab Angleria Mediolonensi. Opera: Legatio babylonica; Occeanea decas; Poemata. Impressum Hispali (Seville): per Jacobu(m) Corumberger alemanu(m), 1511 (Includes only first Decade).
• Petri Martyris. De orbe novo Decades. In illustri oppido Carpetanae p(ro)vinciae Co(m)pluto quod vulgariter dicitur Alcala: in contubernio Arnaldi Guillelmi, 1516 (Includes only first three Decades).
• Petri Martyris ab Angleria Mediolanensis protonotarij Cęsaris senatoris. De orbe novo decades. Compluti: apud Michaele(m) de Eguia, 1530 (First complete edition).
• Petri Martyris ab Angleria Mediolanen. De rebus oceanicis & Orbe nouo decades tres Apud Ioannem Bebelium (Basileae), 1533.
• Peter Martyr of Angleria. The Decades of the Newe Worlde or West India, conteynyng the nauigations and conquestes of the Spanyardes with the particular description of the moste ryche and large landes and Ilandes lately founde in the west Ocean perteynyng to the inheritaunce of the kinges of Spayne […]. Wrytten in the Latine tounge and translated into Englysche by Rycharde Eden. Londini (London): in ædibus Guilhelmi Powell, 1555.
• Peter Martyr d'Anghiera, De orbe novo, translated from the Latin with notes and introduction by Francis Augustus MacNutt (2 vol.), Putnam (New York), 1912.
• Peter Martyr d'Anghiera, Decadas del nuevo mundo, 1944.
• Petrus Martyr de Anghieria, Opera: Legatio Babylonica, De Orbe novo decades octo, Opus Epistolarum, Graz: Akademische Druck- U. Verlagsanstalt, 1966 ISBN 3-201-00250-X

• Peter Martyr map, from the 1511 edition of Decades