Charles IX (Karl IX) (4 October 1550 – 30 October 1611), was King of Sweden from 1604 until his death. He was the youngest son of King Gustav I of Sweden and his second wife, Margaret Leijonhufvud, brother of Eric XIV of Sweden and John III, and uncle of Sigismund III Vasa king of both Sweden and Poland. By his father's will he got, by way of appanage, the Duchy of Södermanland, which included the provinces of Närke and Värmland; but he did not come into actual possession of them till after the fall of Eric and the succession to the throne of John in 1568.
He came into the throne by championing the Protestant cause during the increasingly tense times of religious strife between competing sects of Christianity, where forcible conversion was considered a "best course", a period where the Catholics were growing increasingly belligerent— which, in just over a decade, would break out as the Thirty Years' War—as it had already caused the dynastic squabble rooted in religious freedom that deposed his nephew and brought him to rule as king of Sweden.
With his brother's death in November of 1592, during the era beginning the end (dated 1648 by some) of both the reformation and counter-reformation—the thought processes during the tense political times viewed the inheritance of the throne of protestant Sweden by his devout Roman Catholic nephew and Habsburg ally, Sigismund of Poland and Sweden was viewed with alarm, and several years of religious controversy and discord followed.
During the period, he along with the Swedish privy council ruled in Sigismund's name while he stayed in Poland. After various preliminaries, his nephew was forced to abdicate the throne to Charles IX as regent in 1595 by the Riksens ständer, which eventually kicked off nearly seven decades of sporadic warfare as the two lines of the divided House of Vasa both continued to attempt to remake the union between the Polish and Swedish thrones with opposing counter-claims and dynastic wars.
It is also quite likely, that the dynastic outcome between Sweden and Poland's house of Vasa was a factor which exacerbated and radicalized the later actions of Europe's Catholic princes in the Germanies such as the Edict of Restitution, and so worsened European politics to the abandonment or prevention of settling events by diplomacy and compromise during the vast bloodletting that was the Thirty Years' war.
It was due entirely to him that Sigismund as king-elect was forced to confirm the resolutions at the Uppsala Synod in 1593, thereby recognizing the fact that Sweden was essentially a Protestant state. Under the agreement, Charles and the Swedish Privy Council shared power and ruled in Sigsmunds place since he resided in Poland. In the ensuing years 1593—1595, Charles's task was extraordinarily difficult. He had steadily to oppose Sigismund's reactionary tendencies and directives; he had also to curb the nobility which sought to increase their power at the expense of the absent king, which he did with cruel rigor.
Necessity compelled him to work with the clergy and people rather than the gentry; hence it was that the Riksens ständer (Riksdag) assumed under his regency government a power and an importance which it had never possessed before. In 1595, the Riksdag of Söderköping elected Charles regent, and his attempt to force Klas Flemming, governor of Österland (Finland of the day), to submit to his authority, rather than to that of the king, provoked a civil war. Charles sought to increase his power and the king attempted to manage the situation by diplomacy over several years, until fed up, Sigismund got permission from the Commonwealth's legislature to pursue the matters dividing his Swedish subjects, and invaded with a mercenary army.
Technically Charles was, without doubt, guilty of high treason, and the considerable minority of all classes which adhered to Sigismund on his landing in Sweden in 1598 indisputably behaved like loyal subjects. In the events that followed, despite some initial successes, Sigismund lost the crucial Battle of Stångebro, and was captured himself, as well as forced to deliver up certain Swedish noblemen who were named traitor by Charles and the Riksens ständer. With Sigismund defeated and sent packing, and as both an alien and a heretic to the majority of the Swedish nation, and his formal deposition by the Riksdag of the Estates in 1599 was, in effect, a natural vindication and ex post facto legitimization of Charles's position all along, for the same session of the Riksens ständer named him as the ruler as regent.
Finally, the Riksdag at Linköping, February 24, 1600 declared that Sigismund abdicated the Swedish throne, that duke Charles was recognized as the sovereign under the title of Karl IX of Sweden (Anglicized to Charles IX in the English language). Charles's short reign was one of uninterrupted warfare. The hostility of Poland and the break up of Russia involved him in two overseas contests for the possession of Livonia and Ingria, while his pretensions to claim Lappland brought upon him a war with Denmark in the last year of his reign.
In all these struggles, he was more or less unsuccessful, owing partly to the fact that he and his forces had to oppose superior generals (e.g. Jan Karol Chodkiewicz and Christian IV of Denmark) and partly to sheer ill-luck. Compared with his foreign policy, the domestic policy of Charles IX was comparatively unimportant. It aimed at confirming and supplementing what had already been done during his regency. He did not officially become king until March 6, 1604. The first deed in which the title appears is dated March 20 1604; but he was not crowned until March 15, 1607.
Swedish historians have been excusably indulgent to the father of their greatest ruler. Indisputably Charles was cruel, ungenerous and vindictive; yet he seems, at all hazards, strenuously to have endeavoured to do his duty during a period of political and religious transition, and, despite his violence and brutality, possessed many of the qualities of a wise and courageous statesman.
In 1592 he married his second wife Christina of Holstein-Gottorp (1573-1625), daughter of Adolf of Holstein-Gottorp (1526-1586) and Christine of Hesse (1543-1604) and first cousin of his previous wife. Their children were:
He also had a son with his mistress, Karin Nilsdotter: