Sir Ambrose Jermyn (1511 – 5 April 1577) of Rushbrooke, Suffolk, was an English courtier, magistrate and landowner.^{[1][non-primary source needed]}

Jermyn was the son of Sir Thomas Jermyn (died 1552) of Rushbrooke and Anne Spring, the eldest daughter of Thomas Spring of Lavenham, Suffolk.^[2]

Jermyn inherited his father's Rushbrooke Hall estate following the elder Jermyn's death in 1552. A fervent Roman Catholic, he was knighted by Queen Mary I and served as a Justice of the Peace in Suffolk. In this role he was a notable prosecutor and persecutor of Protestants across East Anglia until the accession of Queen Elizabeth I.^[3] He served as Sheriff of Norfolk and Suffolk in 1558 and 1572.

In 1538 Jermyn married Anne Heveningham, daughter of George Heveningham of Rushbrooke, and his wife Margaret, daughter of John Burgoyne,^[4] by whom he had thirteen children, including:

• Sir Robert Jermyn, eldest surviving son and heir, a Protestant magistrate.^[5] His will was proved in May 1577.^{[6][non-primary source needed]}
• John Jermyn, husband of Mary Tollemache, and father of Thomas Jermyn.^[7]
• Susan Jermyn, wife of Lyonell Tollemache of Helmingham Hall in Suffolk, and mother of Sir Lionel Tollemache, 1st Baronet (1562–c. 1620).