William Frederick, Margrave of Brandenburg-Ansbach (8 January 1686 – 7 January 1723), was Margrave of the Principality of Brandenburg-Ansbach from 1703 until his death in 1723. He was the younger brother of Caroline of Ansbach and thus brother-in-law of George II of Great Britain.
William Frederick was born in Ansbach in 1686 to John Frederick, Margrave of Brandenburg-Ansbach, and his second wife, Eleonore Erdmuthe of Saxe-Eisenach. His two surviving half-brothers, Margraves Christian Albert and George Frederick II, both died unmarried and without legitimate issue.
He married his first cousin, Christiane Charlotte of Württemberg-Winnental. He died in Unterreichenbach and was succeeded by his son Charles William Frederick, called "The Wild Margrave".