Anna Jagiellon

Born 18 October 1523, daughter of Sigismund I the Old and Bona Sforza, Anna fielded marriage proposals for decades but stayed single until 52. Her brother Sigismund II Augustus died without male heirs, ending the Jagiellonian line, and suddenly her hand became the key to dynastic continuity. She was elected co-ruler in 1576 alongside her fiancé Stephen Báthory in a formal, distant marriage. While Báthory waged the Livonian War, Anna managed local administration and oversaw construction projects, including the city wall Stara Prochownia protecting Sigismund Augustus Bridge. Báthory's death in December 1586 left her positioned to rule alone, but she promoted her nephew Sigismund III Vasa instead, seating the House of Vasa on the throne for the next eight decades. She died 9 September 1596.