De origine actibusque Getarum (The Origin and Deeds of the Getae), commonly abbreviated Getica (/ˈɡɛtɪkə/), written in Late Latin by Jordanes in or shortly after 551 AD, claims to be a summary of a voluminous account by Cassiodorus of the origin and history of the Gothic people, which is now lost. However, the extent to which Jordanes actually used the work of Cassiodorus is unknown. It is significant as the only remaining contemporaneous resource that gives an extended account of the origin and history of the Goths, although to what extent it should be considered history or origin mythology is a matter of dispute.

The Getica begins with a discussion of a large island named Scandza, which faces the mouth of the Vistula river and had been described by the writers Claudius Ptolemy and Pomponius Mela. Jordanes reports this island to be the original home of many different peoples including the Goths, who have swarmed like bees from there (16-25). Jordanes commences the history of the Goths with the emigration of a Gothic king named Berig with three ships from Scandza to Gothiscandza (25, 94), in the distant past. In the account of Jordanes (or Cassiodorus), Herodotus' Getian demi-god Zalmoxis becomes a king of the Goths (39). Jordanes tells how the Goths sacked "Troy and Ilium" just after they had recovered somewhat from the war with Agamemnon (108). They are also said to have encountered the Egyptian pharaoh Vesosis (47). The less-fictional part of Jordanes' work begins when the Goths encounter Roman military forces in the 3rd century AD. The work concludes with the defeat of the Goths by the Byzantine general Belisarius, which was recent in the time of Jordanes. Jordanes states that he writes to honour those who were victorious over the Goths after a history of 2030 years.

Because the original work of Cassiodorus has not survived, the work of Jordanes is one of the most important sources for the period of the migration of the European tribes, and the Ostrogoths and Visigoths in particular, from the 3rd century AD. Jordanes mentioned that his work, perhaps via Cassiodorus, also drew upon Gothic "folk songs" (carmina prisca) as an important source, and a Gothic chronicler . Modern scholars have struggled to find any confirming evidence that his claims about such sources can give credibility to the more doubtful parts of the work.

Like many other classical writers, Jordanes equated the earlier Getae to the later Goths. He specified that he did this on the testimony of Orosius Paulus. In a passage that has become controversial, he identifies the Venedi, a people mentioned by Tacitus, Pliny the Elder and Ptolemy, with the Slavs of the 6th century. Since as early as 1844, this passage has been used by some scholars in eastern Europe to support the idea that there was a distinct Slavic ethnicity long before the last phase of the Late Roman period. Others have rejected this view because of the absence of concrete archaeological and historiographical data.

The book is important to some medieval historians because it mentions the campaign in Gaul of one Riothamus, "King of the Brettones", a possible source of inspiration for the early stories of King Arthur.

One of the major questions concerning the historicity of the work is concerning the periods before the Goths enter the written record in the third century. Although there is a range of views, the earliest parts of the narratives are considered mainly mythological, and the account becomes more reliable as it approaches the 6th century. Whether or not Cassiodorus was the main collator of the information about the earliest Goths, not only contains chronologically untenable parts, but also shows evidence of being at least partly derived by culling ancient Greek and Latin authors for descriptions of peoples who might have been Goths. Furthermore, it seems that Jordanes distorted Cassiodorus's narrative by presenting a cursory abridgement of it mixed with 6th-century ethnic names.

Some scholars claim that, while acceptance of Jordanes' text at face value may be too naïve, a totally skeptical view is not warranted. For example, Jordanes writes that the Goths originated in Scandinavia in 1490 BC. Although the chronology is untenable, one Austrian historian, Herwig Wolfram, believes that there might be a kernel of truth in the claim, proposing that a clan of the Gutae may have left Scandinavia and contributed to the ethnogenesis of the Gutones in eastern Pomerania (see Wielbark culture). An example of more believable material concerning the more recent centuries is the name of King Cniva, which David S. Potter thinks is genuine because, since it doesn't appear in the fictionalized genealogy of Gothic kings given by Jordanes, he must have found it in a genuine 3rd-century source.

On the other hand, a Danish scholar, Arne Søby Christensen, claims that the Getica is an entirely fabricated account, and that the origin of the Goths that Jordanes outlines is a construction based on popular Greek and Roman myths, as well as misinterpretation of recorded names from Northern Europe. The purpose of this fabrication, according to Christensen, may have simply been to preserve a memory of a people who, at the time, looked liked they were about to cease to exist. Canadian scholar Walter Goffart suggests another incentive, arguing that the Getica was part of a conscious plan by Justinian I and the propaganda machine at his court to affirm that the Goths and their barbarian cousins did not belong to the Roman world, thus justifying the claims of the Eastern Roman Empire to hegemony over the western part.