Frederick Winsor (October 2, 1829 – February 25, 1889) was a Civil War surgeon, head of the Massachusetts State Hospital and longtime physician in Salem, Massachusetts. Born in Boston, Massachusetts on October 2, 1829, Winsor was the youngest of 12 children of Thomas Winsor (who died when Frederick was two) and Welthea Sprague, one of 15 children of of Duxbury, Massachusetts, a famous Methodist anti-slavery leader.