Mary Spear Nicholas Tiernan (February 14, 1835 - January 13, 1891) was a 19th-century American writer.
Her earliest contributions to literature appeared in Bledsoe's "Southern Review." Her first novel, Homoselle, was the most popular and successful of the "Round Robin Series." Tiernan, encouraged with the reception with which her first novel had met, entered upon an active career, writing for "The Century" and "Harper's Magazine" and publishing two additional novels, Sousette and Jack Horner, 1890.