Sarah Margaret Fuller Ossoli (May 23, 1810 - July 19, 1850), commonly known as Margaret Fuller, was an American journalist, critic, and women's rights advocate associated with the American transcendentalism movement. She was the first full-time American female book reviewer in journalism. Fuller was an advocate of women's rights and, in particular, women's education and the right to employment. She also encouraged many other reforms in society, including prison reform and the emancipation of slaves in the United States. Many other advocates for women's rights and feminism, including Susan B. Anthony, cite Fuller as a source of inspiration. Many of her contemporaries, however, were not supportive, including her former friend Harriet Martineau. She said that Fuller was a talker rather than an activist.

Shortly after Fuller's death, her importance faded; the editors who prepared her letters to be published, believing her fame would be short-lived, censored or altered much of her work before publication.