Maria Carter Syphax, otherwise spelled Mariah (1803 – 1886), was the matriarch of the Syphax family, a prominent family of African Americans in the greater Washington, D.C., area who became civic leaders, civil servants, and educators. She was born into slavery as Maria Carter, daughter of an enslaved woman and George Washington Parke Custis, a grandson of Martha Washington through her first marriage. Syphax was thus a great-granddaughter of First Lady Martha Washington.
Maria Syphax was manumitted by Custis in 1826, along with her two children, and that year he granted her 17 acres of his Arlington plantation. He later bequeathed freedom by his will for her husband Charles Syphax. The family was established as landowning free people of color before the Civil War. Although some of her land was initially confiscated with that of Arlington, her son William Syphax was able to use his connections and gain passage of a relief bill by Congress to return it to her. Her descendants continued to live in the Washington, D.C., area, working as leaders in many civic roles.