Daughter of Polish King and Lithuanian Grand Duke Sigismund I the Old and Italian duchess Bona Sforza, Anna received multiple proposals, but remained unmarried until the age of 52.

After the death of King Sigismund II Augustus, her brother and the last male member of the Jagiellonian dynasty, her hand was sought by pretenders to the Polish-Lithuanian throne to maintain the dynastic tradition.

While Báthory was preoccupied with the Livonian War, Anna spent her time on local administrative matters and several construction projects, including the city wall Stara Prochownia to protect Sigismund Augustus Bridge.

[2] Only after their father's death in 1548, the first serious candidate for a husband emerged – Albert Alcibiades, Margrave of Brandenburg-Kulmbach, but he was a Hohenzollern and a Protestant, had debts and a bad temper.

[3] In the summer of 1548, after a conflict with King Sigismund II Augustus over his secret marriage with Barbara Radziwiłł, Queen Mother Bona and her unmarried daughters moved to Mazovia, mainly Warsaw and Ujazdów Castle.

In 1550, Bona attempted to negotiate marriage with Charles Victor or Philip, sons of Henry V, Duke of Brunswick-Lüneburg, or Prince Ernest of Bavaria.

King Eric XIV of Sweden was personally more interested in pursuing marriage with Queen Elizabeth I of England, but sought an alliance with Poland–Lithuania and suggested his half-brother John, Duke of Finland.

[10] As Vilnius wasn't safe due to the Livonian War, Anna moved to the Royal Castle in Warsaw and lived there for about ten years with a court of about 70 people.

[12] In 1569, a project emerged to marry Anna to Barnim X, Duke of Pomerania, who demanded that she would bring eight border territories as her dowry, which was unacceptable to Poland.

[16] Although Polish-Lithuanian nobles sought to keep her out of the political arena,[14] Anna learned of Henry's offer in spring 1573 and became his strong supporter, flattered that he "cared for her and not only for the Kingdom".

[18] However, due to an oversight (whether intentional or unintentional), Henrician Articles (Henry's pre-election treaty) did not include the promise to marry the Jagiellon heiress and so he tarried.

[19] During the second interregnum, Anna assumed the unprecedented but politically important title of Infanta, mirroring the Spanish custom and highlighting her dynastic status.

[14] Poland did not recognize the status of crown prince since, technically, the monarchy was not hereditary but elective between the native noble families and foreign royalty.

[23] She was skeptical of marriage proposals by Archduke Ernest of Austria, Alfonso II d'Este, Duke of Ferrara, and Frederick IV of Liegnitz.

Although she was forced to surrender the inheritance from her brother after her coronation; in return Anna received some of his properties for her lifetime, Mazovian properties that once belonged to her mother, the treasury kept at Tykocin, a one-time payment of 60,000 gold coins,[27] income from Wieliczka Salt Mine, and interest on her mother's loan to King Philip II of Spain (the loan was never fully repaid and is known as Neapolitan sums).

[31] She supported her husband with money for weapons, but was visibly upset because she sought a closer personal relationship and greater political influence.

[27] There were rumours that he might seek a divorce so he could marry a younger woman and father an heir,[31] which further alienated Anna, who even approached anti-Báthory groups and opposed his Livonian campaign.

Her initial plan, formulated while her husband was still alive, was to wed Anna Vasa to one of the nephews of Stephen Báthory and promote the couple to the throne.

In her campaigns, she wrote numerous letters and used her wealth[33] to gain crucial support from Zamoyski, who was married to Griselda Báthory and held his own ambitions for the throne.