The Uckermark (German pronunciation: [ˈʊkɐˌmaʁk] ^ⓘ) is a historical region in northeastern Germany, which currently^[update] straddles the Uckermark District of Brandenburg and the Vorpommern-Greifswald District of Mecklenburg-Vorpommern. Its traditional capital is Prenzlau.

The region is named after the Uecker River, which is a tributary of the Oder; the name Uckermark means "March of the Uecker". The river's source is close to Angermünde, from where it runs northward to Mecklenburg-Vorpommern. The Oder River, forming the German-Polish border, bounds the region in the east. The western parts of the Lower Oder Valley National Park are located in the Uckermark.

In the Ice Age, glaciers shaped the landscape of the region. A climate change left a hilly area with several lakes formed by the melting ice, and humans started to settle the area. Megalithic-cultures arose, followed by Germanic cultures.

From the 6th–12th centuries Polabian Slavs migrating from Eastern Europe moved westward into the later Uckermark. The Slavs settling the terra U(c)kera (Uckerland, later Uckermark) became known as Ukrani (Ukranen, Ukrer, Ukri, Vukraner). Their settlement area was centered around the lakes Oberuckersee and Unteruckersee at the spring of the Uecker River. In this region, burghs with a proto-town suburbium were set up at Drense and on an isle in Lake Oberuckersee (near modern Prenzlau).

In 954, Margrave Gero of the Saxon Eastern March (the marca Geronis), aided by Holy Roman Emperor Otto I's son-in-law, Conrad of Lorraine, launched a successful campaign to subdue the Ukrani, who had come in reach of the Empire after the 929 Battle of Lenzen. After the 983 revolt of the Obodrites and Liutizians, the area became independent again, yet remained under permanent military pressure, especially from Poland and the Holy Roman Empire.

In 1172 Pomeranian dukes, vassals of the Duchy of Saxony, formerly of Poland, and later of Denmark and the Holy Roman Empire, controlled the area. In the course of the medieval Ostsiedlung, the Ukrani were Christianized and Germanized by Saxons, who founded monasteries, castles, and towns; the Slavic heritage is reflected in the many regional towns whose names end with "-ow" and "-in". The early centers of the territory were the Seehausen (Gramzow) Premonstratensian monastery and the city of Prenzlau, developed and granted German town law by Barnim I, Duke of Pomerania, in 1234. Both the central city and the central monastery were set up beside the former Ukrani central burghs.

The Margraviate of Brandenburg, holding claims on the Duchy of Pomerania, expanded north since the 1230s, taking her chances while the House of Pomerania was weakened. In the 1250 Treaty of Landin, Barnim I conceded the Uckermark to John I and Otto III, Ascanian Margraves of Brandenburg.

After the extinction of the Ascanians, it was contested by several principalities. In 1319 it was seized by Mecklenburg. In 1320 the allied forces of the duchies of Pomerania and Jawor clashed with Mecklenburg in the Uckermark. In late 1320, a portion of the Uckermark was occupied by Saxe-Wittenberg, whereas the northernmost parts with Prenzlau and Pasewalk remained under Pomeranian control. War between Pomerania and Mecklenburg continued in 1322 with Pomerania recapturing Torgelow. Mecklenburg lost her gains in a 1323 war with Brandenburg.