Katherine Willoughby | |
|---|---|
| suo jure Baroness Willoughby de Eresby Duchess of Suffolk | |
 Katherine Willoughby, drawing by Hans Holbein the Younger | |
| Born | 22 March 1519 Parham Old Hall, Suffolk, England |
| Died | 19 September 1580 (aged 61) Grimsthorpe Castle, Lincolnshire, England |
| Noble family | Willoughby |
| Spouse(s) | Charles Brandon, 1st Duke of Suffolk Richard Bertie |
| Issue | Henry Brandon, 2nd Duke of Suffolk Charles Brandon, 3rd Duke of Suffolk Susan Bertie, Countess of Kent Peregrine Bertie, 13th Baron Willoughby de Eresby |
| Father | William Willoughby, 11th Baron Willoughby de Eresby |
| Mother | María de Salinas |
Katherine Brandon, Duchess of Suffolk, suo jure 12th Baroness Willoughby de Eresby (née Willoughby; 22 March 1519 – 19 September 1580), was an English noblewoman living at the courts of King Henry VIII, King Edward VI and Queen Elizabeth I. She was the fourth wife of Charles Brandon, 1st Duke of Suffolk, who acted as her legal guardian during his third marriage to Henry VIII's sister Mary. Her second husband was Richard Bertie, a member of her household. Following Charles Brandon's death in 1545, it was rumoured that King Henry had considered marrying Katherine as his seventh wife, while he was still married to his sixth wife, Catherine Parr, who was Katherine's close friend.
An outspoken supporter of the English Reformation, she fled abroad to Wesel and later the Grand Duchy of Lithuania during the reign of Queen Mary I, to avoid persecution.