Albert (Albrekt av Mecklenburg in Swedish; Albrecht III, Herzog zu Mecklenburg in German) was King of Sweden from 1364 to 1389 and Duke of Mecklenburg-Schwerin from 1384 to 1412 as Albert III.
In 1363, members of the Swedish Council of Aristocracy, led by Bo Jonsson Grip, arrived in the court of Mecklenburg. They had been banished from the country after a revolt against king Magnus Eriksson, who was unpopular among the nobility. At the nobles' request, Albert launched an invasion of Sweden supported by several German dukes and counts. Several Hanseatic cities and dukes in Northern Germany expressed support of the new king. Stockholm and Kalmar, with large Hanseatic populations, also welcomed the intervention.
Albert was proclaimed King of Sweden and officially crowned on 18 February 1364.
The arrival of Albert led to eight years of civil war in Sweden between Albert's and Magnus' supporters. In a battle near Enköping in 1365 between Albert's German forces and king Magnus Eriksson's forces, supported by king Haakon VI of Norway (Magnus' son), Magnus was defeated and taken prisoner by Albert. After the initial defeat, Valdemar IV of Denmark intervened on Magnus and Haakon's behalf, and Valdemar's forces were joined by Swedish peasants who supported Magnus. With the help of Danish and Swedish allies, Haakon managed to temporarily beat back Albert and lay siege to Stockholm in 1371. However, the siege was short-lived; with military help from the Swedish nobility in Stockholm, Albert was able beat back the Norwegians and the Danes. A peace agreement was signed, with the condition that Magnus be released and allowed to freely travel back to Norway (where he spent the rest of his life). Albert had secured the Swedish crown, but was also forced to make a belated coronation oath in which he agreed to extensive concessions to the Swedish nobility in the regency council.
Albert kept the crown of Sweden for another 19 years, but most of western Sweden did not support his reign. However, it was only when he attempted to introduce reduction of the large estates of the Swedish nobility that he lost his support in Stockholm. In 1389, facing a loss of landholdings and wealth, the Swedish regency council turned to Margaret I of Denmark to plead for help in getting rid of Albert. Margaret sent troops and in February 1389, the Danes defeated Albert at the Battle of Åsle (slaget vid Åsle). Albert was captured, deposed and sent to Lindholmen Castle in Scania, where he spent the next six years imprisoned.
Albert died in 1412 and is buried in the monastery of Doberan, Mecklenburg.