Mariana of Austria

Mariana of Austria became Queen of Spain in 1649 when she married Philip IV. Widowed in 1665, she was appointed regent for their infant son Charles II and held power as Spain slid deeper into political chaos and economic crisis. The regency years marked the sharpest phase of Spanish decline in the 17th century, riven by internal fractures and a Europe-wide downturn. Charles never produced an heir; his death in 1700 triggered the War of the Spanish Succession, a 13-year continental bloodbath over who would inherit what remained. She died in 1696, four years before the kingdom she'd managed for so long ignited the continent. The Mariana Islands bear her name from Spain's Pacific expansion during her reign.