The Vetkopers and Schieringers (West Frisian: Fetkeapers en Skieringers) were two opposing Frisian factional parties from the medieval period. They were responsible for a civil war that lasted for over a century (1350–1498) and which eventually led to the end of the so-called "Frisian freedom".

These factional parties arose because of an economic downturn that began in Friesland in the mid-14th century. Accompanied by a decline in monasteries and other communal institutions, social discord led to the emergence of Frisian nobility, who were called haadlingen in East Friesland (headmen) and hoofdelingen in West Friesland. Hoofdelingen were Dutch nobility; they were wealthy landowners who possessed fortified stone houses and a surrounding farming estate (stins and state). The hoofdelingen were farmers who worked for their wealth and status by acquiring farmland and consolidated their positions by holding important local administrative and judicial roles (such as that of grietman).

Frisian politics was largely decentralized at the time. Officially, Friesland had a communal government structure with a central board called the Recht en Raad, which was populated by 30 rural grietmen and 11 city mayors. The real rule, however, was exercised at the local level, in the grietenij, the city, and even in the village. The grietman, which was officially a democratically elected official, were predominantly sourced from the hoofdelingen class. This was because the Hoofdelingen were able to offer military protection to the local inhabitants that lived under the influence of their stins.

From the 1480s it was a common practice that the hoofdelingen nobility established a core militia composed of a few permanent men-at-arms and a few permanent mercenaries, along with an auxiliary force of several hundred inhabitants from the town, city, grietenij or collection of villages over which they held influence. The auxiliary force was formed by huislieden (plural of huisman), which means that they were common people who owned a house, be it as a freeholder or a tenant.

Feuds between hoofdelingen eventually consolidated in aligning along two opposing parties: the Skieringers and the Fetkeapers.

The Schieringer party was led by major hoofdelingen such as the traditional families Harinxma, Sjaerda, Martena, Camstra and Camminga. The Schieringers sought alliances with monarchs such as the Maximilian I of Austria, and his general Albrecht III, Duke of Saxony. The Vetkoper party consisted of a large number of minor hoofdelingen, who were supported by common freehold farmers from the peat areas. The Vetkopers supported self government.

A contemporary Frisian nobleman Jancko Douwama (1482–1533), wrote in his memoirs, titled the Boeck der Partijen ("Book of the Parties") about the origins of the discord between the warring parties in Friesland and his definition of the terms Skieringers and Fetkeapers. According to Jancko the Fetkopers (pronounced [ˈfɛtkoːpərs]; "fat-buyers") were so called because they had much and could buy fat products. The poor adopted the name Skieringers (pronounced [ˈskiːrɪŋərs]; "speakers") because they had tried firstly discussion rather than violence.

In the second half of the fifteenth century the Fetkeaper town of Groningen, which had become the dominating force in Frisia, tried to interfere in Mid-Frisian affairs. The meddling met strong opposition in Skieringer held Westergo and ended in a call for foreign help.