Mary I, eldest daughter of Henry VIII, was Queen of England from 1553 until her death in 1558. For much of this time she ruled alongside her husband, King Philip II of Spain, forming a co-monarchy that put England at the heart of early modern Europe. In this book, Alexander Samson presents a bold reassessment of Mary and Philip's reign, rescuing them from the neglect they have suffered at the hands of generations of historians. The co-monarchy of Mary I and Philip II put England at the heart of early modern Europe. This positive reassessment of their joint reign counters a series of parochial, misogynist and anti-Catholic assumptions, correcting the many myths that have grown up around the marriage and explaining the reasons for its persistent marginalisation in the historiography of sixteenth-century England. Using new archival discoveries and original sources, the book argues for Mary as a great Catholic queen, while fleshing out Philip's important contributions as king of England.