The Travels of Marco Polo, also known as The Book of the Marvels of the World (French: Livres des Merveilles du Monde) and by its Italian name Il Milione ("The Million"), is a 13th-century travelogue written down by Rustichello da Pisa from stories told by the Venetian explorer Marco Polo. It describes Polo's travels through Asia between 1271 and 1295, and his experiences at the court of Kublai Khan.

The book was written by the romance writer Rustichello da Pisa, who worked from accounts which he had heard from Marco Polo when they were imprisoned together in Genoa. Rustichello wrote it in Franco-Venetian, a literary language widespread in northern Italy between the subalpine belt and the lower Po between the 13th and 15th centuries. It was originally known as Livre des Merveilles du Monde or Devisement du Monde ("Description of the World"). The book was translated into many European languages in Marco Polo's own lifetime, but the original manuscripts are now lost, and their reconstruction is a matter of textual criticism. A total of about 150 copies in various languages are known to exist, including in Old French, Tuscan, two versions in Venetian, and two different versions in Latin.

From the beginning, there has been incredulity over Polo's sometimes fabulous stories, as well as a scholarly debate in recent times. Some have questioned whether Marco had actually traveled to China or was just repeating stories that he had heard from other travelers. Economic historian Mark Elvin concludes that recent work "demonstrates by specific example the ultimately overwhelming probability of the broad authenticity" of Polo's account, and that the book is, "in essence, authentic, and, when used with care, in broad terms to be trusted as a serious though obviously not always final, witness."

The source of the title Il Milione is debated. One view is it comes from the Polo family's use of the name Emilione to distinguish themselves from the numerous other Venetian families bearing the name Polo. A more common view is that the name refers to medieval reception of the travelog, namely that it was full of "a million" lies.

Modern assessments of the text usually consider it to be the record of an observant rather than imaginative or analytical traveler. Marco Polo emerges as being curious and tolerant, and devoted to Kublai Khan and the dynasty that he served for two decades. The book is Polo's account of his travels to China, which he calls Cathay (north China) and Manji (south China). The Polo party left Venice in 1271. The journey took three years after which they arrived in Cathay as it was then called and met the grandson of Genghis Khan, Kublai Khan. They left China in late 1290 or early 1291 and were back in Venice in 1295. The tradition is that Polo dictated the book to a romance writer, Rustichello da Pisa, while in prison in Genoa between 1298 and 1299. Rustichello may have worked up his first Franco-Italian version from Marco's notes. The book was then named Devisement du Monde and Livres des Merveilles du Monde in French, and De Mirabilibus Mundi in Latin.

The British scholar Ronald Latham has pointed out that The Book of Marvels was in fact a collaboration written in 1298–1299 between Polo and a professional writer of romances, Rustichello of Pisa. It is believed that Polo related his memoirs orally to Rustichello da Pisa while both were prisoners of the Genova Republic. Rustichello wrote Devisement du Monde in the Franco-Venetian language.

Latham also argued that Rustichello may have glamorised Polo's accounts, and added fantastic and romantic elements that made the book a bestseller. The Italian scholar Luigi Foscolo Benedetto had previously demonstrated that the book was written in the same "leisurely, conversational style" that characterised Rustichello's other works, and that some passages in the book were taken verbatim or with minimal modifications from other writings by Rustichello. For example, the opening introduction in The Book of Marvels to "emperors and kings, dukes and marquises" was lifted straight out of an Arthurian romance Rustichello had written several years earlier, and the account of the second meeting between Polo and Kublai Khan at the latter's court is almost the same as that of the arrival of Tristan at the court of King Arthur at Camelot in that same book. Latham believed that many elements of the book, such as legends of the Middle East and mentions of exotic marvels, may have been the work of Rustichello who was giving what medieval European readers expected to find in a travel book.

Apparently, from the very beginning Marco's story aroused contrasting reactions, as it was received by some with a certain disbelief. The Dominican father Francesco Pipino [it] was the author of a translation into Latin, Iter Marci Pauli Veneti in 1302, just a few years after Marco's return to Venice. Francesco Pipino solemnly affirmed the truthfulness of the book and defined Marco as a "prudent, honoured and faithful man". In his writings, the Dominican brother Jacopo d'Acqui explains why his contemporaries were skeptical about the content of the book. He also relates that before dying, Marco Polo insisted that "he had told only a half of the things he had seen".