Katherine Augusta Westcott Tingley (born July 6, 1847, Newbury, Massachusetts; died July 11, 1929, Visingsö, Sweden) was a social worker and prominent Theosophist. She was the leader, after W. Q. Judge, of the American Section of the Theosophical Society. She founded and led the Theosophical community Lomaland in Point Loma, California.
Tingley grew up in Newbury, Massachusetts. She married Philo B. Tingley in 1888. She was employed as a social worker in New York City when she met William Quan Judge. She joined the Theosophical Society on October 13, 1894.
In 1895, disputes between Judge and Annie Besant led to a split, with Judge taking most of the American section with him, and leading it for one year until his death in 1896. At that point Tingley became the new head of the organization, although her identity was concealed for one year. In 1898, a group of roughly 200 theosophists led by Ernest Temple Hargrove seceded from Tingley's organization, and formed a rival group based in New York City.
On February 13, 1900, she transferred the Society's international headquarters from New York City to a new colony she called Lomaland, located in the Point Loma community near San Diego, California. Her settlement included Raja-Yoga School and College, Theosophical University, and the School for the Revival of the Lost Mysteries of Antiquity.