Catherine Brandon, Duchess of Suffolk, suo jure 12th Baroness Willoughby de Eresby (March 22, 1519 – September 19, 1580), is an English noblewoman living at the royal courts of King Henry VIII, King Edward VI and later, Queen Elizabeth I.
She is the fourth wife of Charles Brandon, 1st Duke of Suffolk, who acts as her legal guardian during his third marriage to Mary Tudor, the younger sister of Henry VIII.
Her second husband is Richard Bertie, a member of her household.
Following Charles Brandon's death in 1545, it is rumored that King Henry is considering marrying Catherine as his seventh wife, while he is still married to his sixth wife, Catherine Parr, who is Catherine's close friend.
An outspoken supporter of the English Reformation, she flees abroad to Wesel and later the Polish–Lithuanian Commonwealth during the reign of Queen Mary I, to avoid persecution.