Sigismund II AugustusArticle Free Pass Sigismund II Augustus,
(born Aug. 1, 1520, Kraków, Pol.—died July 7, 1572, Knyszyn),
last Jagiellon king of Poland, who united Livonia and the duchy
of Lithuania with Poland, creating a greatly expanded and
legally unified kingdom. The only son of Sigismund I the Old and
Bona Sforza, Sigismund II was elected and crowned coruler with
his father in 1530. He ruled the duchy of Lithuania from 1544
and became king of Poland after his father’s death in April
1548. After his first wife died childless (1545), he secretly
married Barbara Radziwiłł, of a Lithuanian magnate family
(1547). When he announced his marriage in 1548, the szlachta
(Polish gentry) tried to force an annulment because it feared
the influence of the Radziwiłłs. He overcame the opposition, but
Barbara died childless in 1551, allegedly poisoned by
Sigismund’s mother. A third marriage (1553), to his first wife’s
sister Catherine, also proved childless, and at his death the
direct Jagiellon line ended. In 1559, w