Elizabeth Trewinnard, Lady Killigrew (b. before 1525; died after 1582), was an aristocratic Cornish woman and an accused pirate during the reign of Queen Elizabeth I of England. She was the wife of Sir John Killigrew of Arwenack, Cornwall. She and her husband received and stored stolen goods at their home, Arwenack House. In 1582, she was arrested and sentenced to death after she sent her servants to seize the cargo aboard a ship anchored in Falmouth harbour. Queen Elizabeth eventually pardoned her, and she was released from prison.
Elizabeth was also known as "Old Lady Killigrew".
Elizabeth was born on an unknown date in St Erth, Cornwall, the second eldest daughter of James Trewinnard (1490-1523), of St Erth, and Philippa Carminow (died 9 August 1563).
She married Sir John Killigrew (died 1567) of Arwenack (Arwenack was sited within the present town of Falmouth which was not founded until 1613), by whom she had a total of ten children:
In the 1540s, Pendennis Castle was built for King Henry VIII on Sir John's lands and the latter became the first hereditary captain of the castle which meant he controlled all of the shipping in the Falmouth area;