The Rhineland or Ripuarian Franks, also often referred to using the Latin plurals Ribuarii, or Ripuarii, were the Franks who established themselves in and around the formerly Roman city of Cologne, on the Rhine river in what is now Germany.

Until the 1950s the Ribuarii were seen as the easternmost of two distinct "sub tribes" of the Franks who ruled two large neighbouring regions in northern Gaul after the collapse of the Roman empire in the fifth century AD. According to this tradition, which continues to be influential, the Ribuarii ruled not just the Rhineland area near Cologne, but all or most of what would later become the Austrasian or Lotharingian region – stretching from present day southern Belgium to the Rhine in present day Germany and the Netherlands. Their western counterparts in this scenario are the Salii, or "Salian Franks", who took control of what is now northern France. This traditional vision of two very large tribes of Franks with large territories is based mainly on two 7th century Frankish legal codes, the Lex Ripuaria and Lex Salica. These laws refer to different geographical jurisdictions, and it was believed that the boundary between them was in the Ardennes and Silva Carbonaria in what is now southern Belgium.

Since the 1950s the term Ripuarian is no longer seen as having its origins as a tribal name, even if it eventually became the name for a specific population based in Cologne. There has also been ongoing scholarly debate about when and how the term Ripuarian was, if ever, applied to the much larger Austrasian region as opposed to the much smaller region around Cologne. The Lex Ripuaria itself is now seen mainly as a law code of the Cologne Rhineland covering such neighbouring towns as Bonn, Zülpich, Jülich and Neuss.

Before the Lex Ripuaria there is a possible mention of the Ripuarii in the 6th-century Byzantine writer Jordanes. In his account of the Battle of the Catalaunian Plains in 451 AD he referred to the Riparii among the units fighting as auxiliaries under the Roman Aetius, against Attila. They are listed together with forces with ethnic designations including Franks, Sarmatians, Armoricans, Burgundians, Saxons. Eugen Ewig argued that these Riparii are not from Cologne, but rather a military unit mentioned in the Notitia Dignitatum, who based on the Rhône river in what is now southern France. Springer however argues against this interpretation, noting that at least three of those four units were naval units, the classis fluminis Rhodani, the classis barcariorum, and the milites musculariorum.

The legal code itself is generally seen as having been made in the 7th century, although it has been argued for example by Springer that it may have been made as late as the early 8th century. It was probably made in the context of the establishment of an Austrasian sub-kingdom by the Merovingians in 623 or 633 AD, possibly as part of a reorganization of the border defence of this kingdom on the Rhine. The Ribuarian area was referred to in Latin using different terms, provincia, ducatus, and regnum and it included the areas around Cologne, Bonn, the Eifel, Zülpich, Jülich, and Neuss. It has been argued that the legal code reveals a deliberate process of "ethnic engineering", aiming to create a Romano-Frankish mixed civilization. According to Springer only the younger manuscripts of the Ribuarian Law Book refer to it as Lex Ribuariorum, named after a people, instead of Lex Ribuaria, named after a country.

Apart from the 7th-century legal code, the earliest narrative source definitely containing a form of the word ribuarius for the people of Cologne is the Liber Historiae Francorum, which was completed about 726/27 AD. The author uses the term terra Riboariense to describe the land (terra) around Cologne which were devastated in 612 AD by the Merovingian king Theuderic II, who defeated his brother Theudebert II at Zülpich and then pursued him to Cologne. After his victory there the author says that the king claimed that one of the "Ribuarians" (Riboariis) in Cologne shot at him. The word was therefore pronounced with a b-like sound at this time and used both as an adjective and a noun, referring to both the region of Cologne, and its inhabitants.

Since the 1950s it has been widely accepted that the plural Ripuarii or Ribuarii, referring to Franks from the Cologne region, did not originate as the name of any Germanic tribe who moved in the so-called Migration period before the 7th century. Instead the name seems to have been connected to the region they moved to. A traditional explanation for the first part of the word comes from Latin rīpa meaning a seashore or riverbank, which is believed to refer in this case to the river Rhine, which runs past Cologne. This explanation remains popular although there is ongoing debate among scholars, both about whether the name is purely derived from Latin, and about whether the name was really intended to refer to the Rhine riverbank.

Latin formations such as ripa-rius, rip-arius, and rip-uarius would all be possible Latin-derived words describing a person of the riverbank, but purely Latin explanations of the word are generally avoided among scholars, because the second part of the name seems to be the same as the suffix found in several other Germanic tribal names such as the Ampsivarii, Chasuarii, and Angrivarii. This suffix -varii is normally believed to come not originally from Latin, but from a Germanic word meaning inhabitants. A version of this suffix is for example found in Old English, in words like Rōmware, meaning inhabitants of Rome.