This paper re-examines Queen Bona Sforza (1494–1557) as an active co-ruler of early modern Poland, challenging traditional notions of queenship. Through analysis of diplomatic correspondence, administrative reforms, and economic policies, it highlights Bona's significant political agency alongside King Sigismund I. By investigating her political strategies, diplomacy and alliances, territorial governance, and economic and fiscal innovations, the paper aims to reconceptualise the broader concepts of dynasty and rulership, contributing new insights to debates on gender and power in Early Modern Europe.