Catherine de' Medici, queen of Henry II of France (b. 1519)
Catherine de' Medici (Italian: Caterina de' Medici, pronounced [kateˈriːna de ˈmɛːditʃi]; French: Catherine de Médicis, pronounced [katʁin də medisis]; 13 April 1519 – 5 January 1589) was an Italian noblewoman born into the Medici family. She was Queen consort of France from 1547 until 1559, by marriage to King Henry II, and mother of French kings Francis II, Charles IX and Henry III. The years during which her sons reigned have been called "the age of Catherine de' Medici" as she had extensive, if at times varying, influence in the political life of France.Catherine was born in Florence to Lorenzo de' Medici, Duke of Urbino, and Madeleine de La Tour d'Auvergne. In 1533 at the age of fourteen, Catherine married Henry, second son of King Francis I and Queen Claude of France. Catherine's marriage was arranged by her uncle Pope Clement VII. Henry excluded Catherine from participating in state affairs and instead showered favours on his chief mistress, Diane de Poitiers, who wielded much influence over him. Henry's death in 1559 thrust Catherine into the political arena as mother of the frail 15-year-old King Francis II. When Francis II died in 1560, she became regent on behalf of her 10-year-old son King Charles IX and was thus granted sweeping powers. After Charles died in 1574, Catherine played a key role in the reign of her third son, Henry III. He dispensed with her advice only in the last months of her life and outlived her by seven months.

Catherine's three sons reigned in an age of almost constant civil and religious war in France. The problems facing the monarchy were complex and daunting. However, Catherine was able to maintain the monarchy and the state institutions functioning—even at a minimum level. At first, Catherine compromised and made concessions to the rebelling Calvinist Protestants, or Huguenots, as they became known. However, she failed to fully grasp the theological issues that drove their movement. Later she resorted (in frustration and anger) to hard-line policies against them. In return, she came to be blamed for the persecutions carried out under her sons' rule, and in particular, for the St. Bartholomew's Day massacre of 1572, during which thousands of Huguenots were killed both in Paris and throughout France.

Some historians have excused Catherine from blame for the worst decisions of the crown, though evidence for her ruthlessness can be found in her letters. In practice, her authority was always limited by the effects of the civil wars. Therefore, her policies may be seen as desperate measures to keep the Valois monarchy on the throne at all costs and her patronage of the arts as an attempt to glorify a monarchy (whose prestige was in steep decline). Without Catherine, it is unlikely that her sons would have remained in power. According to Mark Strage, one of her biographers, Catherine was the most powerful woman in 16th-century Europe.