Margaret was Duchess of Parma from 1547 to 1586 as the wife of Duke Ottavio Farnese and Governor of the Netherlands from 1559 to 1567 and from 1578 to 1582. She was the illegitimate daughter of Charles V, Holy Roman Emperor, and Johanna Maria van der Gheynst. She had briefly been Duchess of Florence from 1536 to 1537 by her first marriage to Alessandro de' Medici, Duke of Florence.

Ottavio Farnese reigned as Duke of Parma and Piacenza from 1547 until his death and Duke of Castro from 1545 to 1547 and from 1553 until his death.