American abolitionist who was the principal lieutenant of the radical antislavery leader William Lloyd Garrison (Garrison, William Lloyd).

Maria Weston spent several years of her youth living with the family of an uncle in England, where she received a good education. From 1828 to 1830 she was principal of the Young Ladies' High School in Boston. Her marriage in 1830 to Henry Grafton Chapman, a Boston merchant, brought her into abolitionist circles, and in 1832 with 12 other women she founded the Boston Female Anti-Slavery Society. In 1835, as a violent mob was about to disrupt the group's meeting, Maria Chapman uttered a statement long quoted by abolitionists: “If this is the last bulwark of freedom, we may as well die here as anywhere.”

Chapman became chief assistant to Garrison, helping him to run the Massachusetts Anti-Slavery Society and to edit The Liberator, a widely-circulated abolitionist publication. In 1839 she published Right and Wrong in Massachusetts, a pamphlet that argued that the deep divisions among abolitionists stemmed from their disagreements over women's rights. From 1839 to 1842 she also edited the Non-Resistant, the publication of Garrison's New England Non-Resistance Society. Chapman raised funds for the abolition movement (abolitionism) by organizing antislavery fairs throughout New England.

In 1836 Chapman published a collection of Songs of the Free and Hymns of Christian Freedom. In May 1838 she addressed the Anti-Slavery Convention of American Women in Philadelphia in defiance of a threatening mob. (The mob returned the next day and burned down the hall.) In 1877 she published an edition of the autobiography of the English writer Harriet Martineau, an old friend, to which she appended a lengthy memoir. The essayist and poet John Jay Chapman (Chapman, John Jay) was her grandson.