Swedish jarls

In Sweden, members of medieval royal families, such as the House of Stenkil and House of Bjelbo, held the title of jarl before their accession to the throne. Since the early 12th century, there usually was only one holder of the title at a time, second only to the King of Sweden.

For special occasions, regional jarls outside of Sweden could be nominated as well. An example of this is Jon Jarl, who allegedly conducted pirate operations against Novgorod in the east. When the House of Bjelbo (alt. Bjälbo) succeeded in becoming the royal family in 1250, the title was subsumed into that of duke and the powers were merged into the kingship soon after Birger Jarl's death in 1266.

History
According to Procopius, the Heruli, after having raided the European continent for several generations, returned to Scandinavia in 512 as a result of military defeats. As their old territory was now occupied by the Danes, they settled next to the Geats in present-day Sweden. While the Proto-Norse word for this mysterious tribe, erilar, is etymologically near the title "jarl" and "earl" in other places, perhaps implying ' those who can read or dictate ' and it has often been suggested they introduced the runes in Scandinavia, no elaborate theory exists to explain how the word came to be used as a title. Arguably, their knowledge in interpreting runes also meant they were gifted in martial arts and, as they gradually integrated, eril or jarl instead came to signify the rank of a leader. As described in the Icelandic sagas, such as Rígsthula, a jarl was a sort of chieftain next in rank to the king in the function of Marshal or Duke of the King's Army. Under any circumstance, when jarls are finally mentioned in medieval documents, it clearly was a title signifying a leader ranked directly under the king.

In Swedish history, Jarls are described as either local rulers or viceroys appointed by a king, ruling one of the historical Swedish provinces, such as Västergötland, Östergötland, or Svitjod. In Norway, the jarls apparently kept this role and the kings attempted to introduce one in each Fylke before the title was used exclusively on the Orkney Islands in the 14th century. In Sweden, however, by the mid-10th century the title was used exclusively by a single person and the local leaders were gradually being referred to as dux or duke. Before the title was finally discontinued in the mid-13th century, Swedish jarls were powerful men, such as Birger Brosa, Ulf Fase, and Birger Jarl (actual surname "Magnusson"), often the true rulers of the Swedish kingdom.

Jarls of Sweden
From diverse families:
 * Jon Sverkersson, eldest son and heir of king Sverker I of Sweden
 * Karl Sverkersson, next son of king Sverker I - jarl in Gothenland
 * jarl Ragvald Henriksson, riksjarl during the brief reign of his brother Magnus (II)
 * Ulf Jarl, jarl in 1020s
 * jarl Guttorm, in 1160s

From the House of Bjelbo:
 * Folke the Fat, jarl around 1100
 * Bengt Snivil, jarl in the mid-12th century - probably never jarl
 * Birger Brosa, 1174-1202
 * Johan Sverkersson, 1202-120?
 * Jon Jarl, ?-1206?
 * Knut Birgersson, 120?-1208, killed in 1208 at the Battle of Lena
 * Folke Birgersson, 1208-1210, killed in 1210 at the Battle of Gestilren
 * Charles the Deaf (Karl Döve), 1210?-1220, killed at the Battle of Lihula
 * Ulf Fase, 1220?-? and 1231–1240, died 1248
 * Birger Magnusson, 1248-1266, last jarl (Dux Sweciae)

Jarls of Västergötland
From the House of Stenkil:
 * Ulf Tostesson
 * Ragnvald Ulfsson (c. 1010-20), later jarl of Staraja Ladoga and Ingria. Father of king Stenkil of Sweden.

Other

 * Jon Jarl (possibly several ones)
 * Roger I of Sicily (Jarl Rogeirr)

In popular culture

 * In The Elder Scrolls V: Skyrim, the term Jarl is used for local lords, keeping in tune with Norse Mythology motifs.
 * In the historical role playing video game Mount&Blade: Warband, lords of Kingdom of Nords, a faction inspired by medieval Nordic cultures, are titled Jarls.
 * In the History Channel's historical drama television series Vikings, actor Thorbjørn Harr plays the character of Jarl Borg, a Jarl of Götaland.
 * In The Witcher 3: Wild Hunt, there is a community led by Jarls based on historical Vikings and Scotsman on the islands of "Skellige".