The Geography (Ancient Greek: Γεωγραφικὴ Ὑφήγησις, Geōgraphikḕ Hyphḗgēsis, lit. "Geographical Guidance"), also known by its Latin names as the Geographia and the Cosmographia, is a gazetteer, an atlas, and a treatise on cartography, compiling the geographical knowledge of the 2nd-century Roman Empire. Originally written by Claudius Ptolemy in Greek at Alexandria around 150 AD, the work was a revision of a now-lost atlas by Marinus of Tyre using additional Roman and Persian gazetteers and new principles.

Its translation into Arabic by al-Khwarismi in the 9th century was highly influential on the geographical knowledge and cartographic traditions of the Islamic world. Alongside the works of Islamic scholars—and the commentary containing revised and more accurate data by Alfraganus—Ptolemy's work was subsequently highly influential on Medieval and Renaissance Europe.

Versions of Ptolemy's work in antiquity were probably proper atlases with attached maps, although some scholars believe that the references to maps in the text were later additions.

No Greek manuscript of the Geography survives from earlier than the 13th century. However fragmentary papyri of later somewhat derivative works such as the Table of Noteworthy Cities have been found with the earliest, Rylands Library GP 522, dating to the early 3rd century. A letter written by the Byzantine monk Maximus Planudes records that he searched for one for Chora Monastery in the summer of 1295; one of the earliest surviving texts may have been one of those he then assembled. In Europe, maps were sometimes redrawn using the coordinates provided by the text, as Planudes was forced to do. Later scribes and publishers could then copy these new maps, as Athanasius did for the emperor Andronicus II Palaeologus. The three earliest surviving texts with maps are those from Constantinople (Istanbul) based on Planudes's work.

The first Latin translation of these texts was made in 1406 or 1407 by Jacobus Angelus in Florence, Italy, under the name Geographia Claudii Ptolemaei. It is not thought that his edition had maps, although Manuel Chrysoloras had given Palla Strozzi a Greek copy of Planudes's maps in Florence in 1397.

Berggren & Jones (2000) place these manuscripts into a stemma whereby U, K, F and N are connected with the activities of Maximos Planudes (c.1255-1305). From a sister manuscript to UKFN descends R, V, W & C, however the maps were either copied defectively or not at all. "Of the greatest importance for the text of the Geography" they state is manuscript X (Vat.Gr.191); "because it is the only copy that is uninfluenced by the Byzantine revision." e.g. the 13th-14th century corrections of Planudes, possibly associated with recreating the maps.

Regarding the maps, they conclude that it was unlikely that extant maps survived from which the above stemma descends, even if maps existed in antiquity:

"The transmission of Ptolemy's text certainly passed through a stage when the manuscripts were too small to contain the maps. Planudes and his assistants therefore probably had no pictorial models, and the success of their enterprise is proof that Ptolemy succeeded in his attempt to encode the map in words and numbers. The copies of the maps in later manuscripts and printed editions of the Geography were reproduced from Planudes' reconstructions."