X Reais - Sebastião I

Sebastião I came to the Portuguese throne as a three-year-old in 1557, with his grandmother Catherine of Austria serving as regent until 1562 and Cardinal Henry thereafter. Copper coinage of this reign circulated against a backdrop of aggressive imperial overextension — Sebastião's obsession with a crusade against Morocco culminated at Alcácer Quibir in 1578, where he died without an heir, triggering the Iberian Union under Philip II of Spain just two years later.

The dynastic collapse that followed effectively ended independent Portuguese monetary policy for sixty years.