thumb|right|300px|Map of the [[Roman Empire and surrounding peoples in AD 125. The map shows two possible locations of the Fenni, based on possible readings of Tacitus (Livonia) and Ptolemy (upper Vistula river). Another location given by Ptolemy, in northern Scandinavia, is not shown as the map does not cover that region]]
The Fenni were an ancient people of northeastern Europe, first described by Publius Cornelius Tacitus in Germania in 98 CE.
Ancient accounts
The Fenni are mentioned in a short reference in Tacitus' Germania: "The Venedi overrun in their predatory excursions all the woody and mountainous tracts between the Peucini and the Fenni". The Greco-Roman geographer Ptolemy, who produced his Geographia in ca. 150 CE, mentions a people called the Phinnoi (Φιννοι), generally believed to be synonymous with the Fenni. He locates them in two different areas: a northern group in northern Scandia (Scandinavia), then believed to be an island; and a southern group, apparently dwelling to the East of the upper Vistula river (SE Poland). It remains unclear what was the relationship between the two groups.
The next ancient mention of the Fenni/Finni is in the Getica of 6th-century chronicler Jordanes. In his description of the island of Scandza (Scandinavia), he mentions three groups with names similar to Ptolemy's Phinnoi, the Screrefennae, Finnaithae and mitissimi Finni ("softest Finns"). The Screrefennae is believed to mean the "skiing Finns" and are generally identified with Ptolemy's northern Phinnoi and today's Finns. The Finnaithae have been identified with the Finnveden of southern Sweden. It is unclear who the mitissimi Finni was.
Ethno-linguistic affiliation
Tacitus was unsure whether to classify the Fenni as Germanic or Sarmatian. Against this argument is the fact that Tacitus distinguishes the Fenni from other probably non-Germanic peoples of the region, such as the Aestii and the Veneti.
It has also been suggested that Tacitus' Fenni could be the ancestors of the modern Finnish people. Juha Pentikäinen writes that Tacitus may well have been describing the Sámi or the proto-Finns when referring to the Fenni, noting some archeologists have identified these people as indigenous to Fennoscandia. The context of Fenni has also included the Finnic Estonians throughout different interpretations. Nevertheless, according to some linguists, certain linguistic evidence may be interpreted supporting the idea of an archaic Indo-European dialect and unknown Paleo-European languages existing in north-eastern Baltic Sea region before the spread of Finno-Ugric languages like Proto-Sámi and Proto-Finnic in the early Bronze Age around 1800 BCE. However, in Tacitus's time (1st century CE) Finno-Ugric languages (Proto-Sámi and Proto-Finnic) were the main languages in northern Fennoscandia.
Another theory is that Tacitus' Fenni and Ptolemy's northern Phinnoi were the same people and constituted the original Sámi people of northern Fennoscandia, making Tacitus' description the first historical record of them, and the mention of two different "Phinnoi" groups may suggest that there was already a division between Finns and Sámi. But while this may seem a plausible identification for the Phinnoi of northern Scandinavia, it is dubious for Tacitus' Fenni. Tacitus' Fenni (and Ptolemy's southern Phinnoi) were clearly based in continental Europe, not in the Scandinavian peninsula, and were thus outside the modern range of the Sámi. Against this, there is some archaeological evidence that the Sámi range may have been wider in antiquity. Sámi place names are found as far as Southern Finland and Karelia
The uncertainties have led some scholars to conclude that Tacitus' Fenni is a meaningless label, impossible to ascribe to any particular region or ethnic group. But Tacitus appears to relate the Fenni geographically to the Peucini(Bastarnae) and the Venedi, albeit imprecisely, stating that the latter habitually raided the "forests and mountains" between the other two. He also gives a relatively detailed description of the Fenni's lifestyle. although Vladimir Orel viewed its etymology as unclear and listed a couple of alternative proposals (i.e. a derivation from Proto-Celtic *þenn- "hill"). Tacitus describes the Fenni as follows: