Susan Mary Brown Alexander (June 20, 1828 – December 19, 1910) was a prominent Presbyterian churchwoman and missionary supporter who was active in religious and benevolent work throughout her life as noted in her obituary in The New York Observer. She was the daughter of Rev. Matthew Brown, long-time president of Washington & Jefferson College, and in 1849 married Henry Martin Alexander, with whom she raised a family including leaders in the Presbyterian community. Mrs. Alexander was deeply involved in church benevolence and missionary activities, was widely respected in her denomination, and is buried in Princeton Cemetery, Princeton, New Jersey.