Frederica Mildmay, Countess FitzWalter

Frederica Susanna Mildmay, Countess FitzWalter (c.1688, Berlin–7 August 1751) was a British peeress.

Frederica was the eldest surviving daughter of Meinhardt Schomberg, 3rd Duke of Schomberg and his second wife, Karoline, a daughter of Charles I Louis, Elector Palatine. On 26 May 1715, she married the 3rd Earl of Holderness and they had two surviving children: Hon. Robert (1718-1778) and Lady Caroline (d. 1778, married the 4th Marquess of Lothian).

On the death of the countess' father in 1719, she inherited his Portuguese countship of Mértola as his eldest surviving child. Her husband died in 1721 and on 18 June 1724, she married Hon. Benjamin Mildmay, who was later created Earl FitzWalter in 1730.