Katharina Lohrenz Schellenberg (1870 – January 1, 1945) was an American Mennonite medical missionary of Russian birth.

Schellenberg was born in a colony of Tiegerweide, at the time in South Russia, today village Mostove, Tokmak Raion in Ukraine; it was part of the Molotschna Mennonite colony. Her parents were Abraham and Katharina Lohrenz Schellenberg, with whom she immigrated to the United States in 1879, settling in Kansas.^[1] When she was fourteen, her mother died. At nineteen, she made her first commitment to Christ, joining the Mennonite congregation in Buhler, Kansas.^[2] Schellenberg studied medicine at the Deaconess Hospital in Cleveland, an undertook further study at the Medical Institute of Homeopathic Medicine in Kansas City, Kansas; she was the first woman among North American Mennonites to become a doctor, and became the denomination's first medical missionary in India when she traveled to that country in 1907.^[1] She learned to speak Telugu as part of her preparations. Early in her career she worked in various locations, from Hughestown as far south as the Tungabhadra River; the mission built a hospital at Nagarkurnool in 1912.^[3] The 1928 completion of another hospital, in Shamshabad, meant that city became her home base. Many of her patients were Muslim women who could not be seen by a male doctor. Schellenberg died suddenly in India, and is buried in the St. George Cemetery in Hyderabad.^[2] An archive of photographs related to her career in India is held at the Mennonite Library & Archives at Fresno Pacific University.^[4]