Anna Jagiellon (, ; 1523–1596) was
Queen of Poland and
Grand Duchess of Lithuania in her own right from 1575 to 1586. She was a daughter of Polish King Sigismund I the Old and his Italian wife
Bona Sforza. Despite multiple proposals, she remained unmarried until the age of 52. After the death of King
Sigismund II Augustus, her brother and the last male member of the
Jagiellon dynasty, Anna's hand was sought by pretenders to the Polish–Lithuanian throne to maintain the dynastic tradition. She was
elected, along with her then-fiancé
Stephen Báthory, as co-ruler in the
1576 royal election of the
Polish–Lithuanian Commonwealth. Their marriage was a formal arrangement and distant. Báthory was preoccupied with the
Livonian War, while Anna spent her time in Warsaw on local administrative matters and several construction works. After Báthory's death in December 1586, she had an opportunity to claim the throne for herself (she was co-ruler and not merely a consort), but did not even attempt it. Instead, she promoted her nephew
Sigismund III Vasa, establishing
House of Vasa on the Polish–Lithuanian throne for the next eighty years (1587–1668).