19th-century American writer whose work on Native Americans, though coloured by her time and circumstance, was drawn from personal experience of her subjects.

In 1835 Mary Henderson, the granddaughter of Commodore Thomas Truxtun, a hero of the naval war with France, married Lieutenant Seth Eastman, an army officer then on the faculty at West Point. Six years later she accompanied her husband to the Minnesota Territory, where he took command of Fort Snelling. Eastman thus had the opportunity to observe the Mdewkanton Sioux of the region. This experience was reflected in her Dahcotah; or, Life and Legends of the Sioux Around Fort Snelling (1849), which was later said, on little real evidence, to have influenced Henry Wadsworth Longfellow (Longfellow, Henry Wadsworth)'s Song of Hiawatha. Also in 1849 the Eastmans moved to Washington, D.C.

In 1852 Eastman published Aunt Phillis's Cabin; or, Southern Life as It Is, a hastily composed answer to Harriet Beecher Stowe's Uncle Tom's Cabin in which she stoutly defended the South and the institution of slavery. The book brought her considerable fame. A series of tales published in the periodical press was collected in The Romance of Indian Life (1853), which was followed by The American Aboriginal Portfolio (1853) and Chicora and Other Regions of the Conquerors and the Conquered (1854; republished in 1855 as The American Annual: Illustrative of the Early History of North America), all of which were illustrated by her husband. Her writings on Native Americans, although often sentimental and to some extent shaped by commonplace prejudices, had the invaluable advantage of being drawn from firsthand knowledge. Unlike many writers in the field, Eastman had taken the time to learn the language of her subjects. From 1855 to 1867 she and her husband were much apart as his duties took him from place to place while she and her children remained mainly in Washington, D.C. During that time she wrote little. In 1879, four years after her husband's death, however, she published Easter Angels, a verse work.