Jacob Kettler
Duke of Courland and Semigallia
Reign17 August 1642 – 1 January 1682
PredecessorFrederick Kettler
SuccessorFrederick Casimir Kettler
Born(1610-10-28)28 October 1610
Goldingen (Kuldīga)
Died1 January 1682(1682-01-01) (aged 71)
Mitau (Jelgava)
Ducal crypt in the Jelgava Palace
SpouseMargravine Louise Charlotte of Brandenburg
IssueLadislaus Louis Frederick Kettler
Frederick Casimir Kettler
Charles Jacob Kettler
Ferdinand Kettler
Alexander Kettler
Louise Elisabeth, Landgravine of Hesse-Homburg
Christina Sophia Kettler
Charlotte Sophia Kettler, Abbess of Herford
Maria Amalia, Landgravine of Hesse-Kassel
FatherWilhelm Kettler
MotherDuchess Sophie of Prussia

Jacob Kettler (German: Jakob von Kettler, Latvian: Hercogs Jēkabs Ketlers; 28 October 1610 – 1 January 1682) was a Baltic German Duke of the Duchy of Courland and Semigallia (1642–1682). Under his rule, Courland and Semigallia became more independent of its Polish suzerain, reached its peak in wealth, and even engaged in its own overseas colonization, making it one of the smallest, but fastest growing states in the world at that time.

Yet, in the end the results of his rule failed in the confrontation with much stronger powers both directly in the Baltic (Sweden) and overseas (Dutch Republic). A ruler "too rich and powerful to be a duke but too small and poor to be a king"[1] could not, with his small ancestral territory and very limited resources, play the powerful role he sought in European politics of that time.

Early life

Kettler was born in Goldingen (now known as Kuldīga). He was the son of Wilhelm Kettler and Duchess Sophie of Prussia, a daughter of Albert Frederick, Duke of Prussia, and was a godson of King James I of England. While his father was exiled from the duchy, Jacob lived in the courts of Stettin and Berlin. He studied in Rostock and at the University of Leipzig and sympathized with the ideas of mercantilism.

In 1633, he led a Curonian regiment in the Smolensk War between the Polish–Lithuanian Commonwealth and Russia. In 1634, he made a grand tour of Europe, visiting Paris, London, and Amsterdam, where he studied shipbuilding. In 1638, he became co-ruler of the duchy and in 1642 sole Duke of Courland.


Jacob Kettler's thaler, 1645

Under Kettler's rule, the duchy traded with the Netherlands, Portugal, England, France, and other nations. He started large scale reforms of the duchy's economy, improved its agriculture, opened many manufactures and started a shipbuilding industry. He founded the Fleet of Courland and Semigalla, a navy and merchant fleet. During his reign, the duchy became de facto independent of the Polish crown, because all contracts with foreign powers were signed as between independent states. After 1646, all customs administration of the duchy also was in the duke's power.

The duchy was involved in colonisation. In 1651 Jacob sent a fleet to build Fort Jacob on the Gambia River, on an island that would later be known as Kunta Kinteh Island. In 1654, he conquered Tobago with forces from the Das Wappen der Herzogin von Kurland, a double-decker ship armed with 45 cannons, carrying 25 officers, 124 Courlander soldiers, and eighty families of Latvian colonists. The colony on Tobago was named Neu Kurland ('New Courland' in German). In 1654, Duke Jacob was a party to the Treaty of Westminster.


The duke was taken prisoner by the Swedes from 1658 to 1660, during the Northern Wars. Together with his family, he was held captive in Riga and later in Ivangorod. During this time, his colonies were attacked and lost and his fleet destroyed. After the war ended, he rebuilt the duchy's fleet and retook the island of Tobago from the Dutch. Some believe[weasel words] he also intended to colonize Australia, which had at that time been discovered and claimed by the Dutch, with whom he was at war.[citation needed] He supposedly had the blessing of Pope Innocent X.[citation needed]

However, the pope soon died, and the new pope was unwilling to support the plan.[citation needed] For the rest of his reign he tried to reach a pre-war level of wealth but managed to do this only partly.

The duke died in Mitau (Jelgava) on 1 January 1682.


Kettler is remembered as a fair ruler who gave opportunities to the local Latvian peasants and even knew the Latvian language.[1]

Marriage and issue

Kettler married Princess Louise Charlotte of Brandenburg (1617–1676), the daughter of George William, Elector of Brandenburg and had issue:[2]

Name Birth Death Notes
Louise Elisabeth Kettler 12 August 1646 16 December 1690 married Frederick II, Landgrave of Hesse-Homburg; had issue; died aged 44
Ladislaus Louis Frederick Kettler 14 December 1647 31 March 1648 died aged 3 months
Christina Sophia Kettler 15 May 1649 9 June 1651 died aged 2
Frederick II Casimir Kettler 6 July 1650 22 January 1698 married (1) Countess Sophie Amalie of Nassau-Siegen; had issue (2) Margravine Elisabeth Sophie of Brandenburg; had issue; died aged 48
Charlotte Sophia Kettler 17 September 1651 1 December 1728 never married; became the Abbess in Herford; died aged 76
Maria Amalia Kettler 12 June 1653 16 June 1711 married Charles I, Landgrave of Hesse-Kassel; had issue; died aged 58
Charles Jacob Kettler 20 October 1654 29 December 1677 never married; died aged 23
Ferdinand Kettler 2 November 1655 4 May 1737 married Princess Johanna Magdalene of Saxe-Weissenfels; no issue; died aged 81
Alexander Kettler 16 October 1658 28 June 1686 never married; died aged 27



  1. ^ a b "The ambitious journey of Duke Jacob Kettler". History & Culture Academy of Latgale. Retrieved 25 July 2019.
  2. ^ Jakob Kettler, Duke of Kurland & Semgallen in: Our Royal, Titled, Noble, and Commoner Ancestors & Cousins (over 164,000 names) [retrieved 8 May 2015].
Preceded byFriedrich Kettler Duke of Courland 1642–1682 Succeeded byFrederick Casimir Kettler