Ebenhaeser (also Ebenezer) Theodore Stegmann, mathematician, was the son of George Frederick Stegmann, a farmer, and his wife Elsje Johanna van Heerden. He attended the Boys' Public School, Malmesbury, and passed the matriculation examination of the University of the Cape of Good Hope in 1908. Continuing his studies at Victoria College, Stellenbosch, he distinguished himself both as a rugby player and as a student, being awarded the BA degree with honours in applied mathematics by the University of the Cape of Good Hope in 1911. He then proceeded to Germany and continued his studies in mathematics at the University of Gottingen. However, his studies were disrupted by the outbreak of World War I (1914-1918). He returned to South Africa in 1914 and was awarded the DSc degree by the University of the Cape of Good Hope in 1916 with a thesis entitled The torsion problem for bodies of revolution. His thesis was subsequently published under the same title in the Transactions of the Royal Society of South Africa (1918/9, Vol. 7, pp. 147-181).
In 1916 Stegmann was appointed as a lecturer in applied mathematics at Victoria College (from 1918 the University of Stellenbosch) where he assisted Professor J.T. Morrison*. He was promoted to professor of mathematics in July 1920, succeeding Professor A.B. Bartmann*, and held this post until his death in 1957. During these years he introduced Afrikaans as a language of instruction in mathematics at Stellenbosch and made important contributions to the development of an Afrikaans terminology of mathematics. Except for his thesis he does not appear to have published any papers, though he did write a textbook for schools, Introduction to trigonometry (Stellenbosch, 1920; also available in Afrikaans).
Stegmann was a member of the Royal Society of South Africa and, from 1917, of the South African Association for the Advancement of Science. He served on the university council from 1929 to 1948, represented the university on the Matriculation Board for many years and acted as moderator in mathematics for all the matriculation examining bodies. From 1952 until his death he was a member of the Council for Scientific and Industrial Research (CSIR). He was a tall, athletic man who devoted his spare time to woodwork, hunting and fishing. He married Hester Anna Frederika de Waal, with whom he had two daughters.