Cynthia Ann Stanton Baum (28 October 1820 – 1905) was L. Frank Baum's mother.

Her father Oliver Stanton was a successful farmer of Scotch/Irish descent. When Cynthia, the youngest of his six children, was courted by Benjamin Ward Baum in the early 1840s, Oliver Stanton did not favor a match between his daughter and a poor cooper. The two young people eloped on 10 March 1843, when both were 21 years old.

Over the next two decades the Baums had nine children, five of whom survived to adulthood. [See: Baum's siblings.]

Cynthia Baum was a devout Methodist throughout her life; her unorthodox son regularly teased her on religious subjects. For six weeks in 1896, Cynthia Baum visited her son's family, at a time when Baum's mother-in-law Matilda Joslyn Gage was also a visitor. Perhaps unsurprisingly, the feminist Gage did not get along with the more conventional Baum, and in her correspondence described Cynthia Baum as behaving "like a child."

Baum did change his behavior for his mother in at least one particular: when she was visiting, he refrained from attending Chicago Cubs baseball games on Sundays.

In her old age, Cynthia Baum was cared for by her youngest son Henry Clay Baum.

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