Tore Olaus Engset (May 8, 1865 – October, 1943 in Oslo) was a Norwegian mathematician and engineer who did pioneering work in the field of telephone traffic queuing theory.

Tore Olaus Engset was born at Stranda in Møre og Romsdal, Norway. After he graduated school at the age of 18, Engset was admitted to the telegraph school in Stavanger in 1883. He received his certificate in a year and took employment. In his spare time he continued his studies, graduating in 1892 but continuing his university studies. Engset received an M.Sc. in physics and mathematics in 1894 at University of Oslo, after which he worked at Televerket as office worker, traffic analyst and from 1921–22 and 1930–35 director general.

He developed the Engset formula in 1915, before the breakthroughs of A. K. Erlang from 1917. His 1915 manuscript "Om beregningen av vælgere i et automatisk telefonsystem" (1915) was not, however, published until 1918. That work was translated to German as "Die Wahrscheinlichkeitsrechnung zur Bestimmung der Wählerzahl in automatischen Fernsprechämtern", in Elektrotechnische Zeitschrift, Heft 31, 1918. An English translation appeared in Arne Myskja, "On the Calculation of Switches in an Automatic Telephone System" in Telektronikk, 94(2):99-142, 1998.

He also published a work on nuclear physics (1927): "Die Bahnen und die Lichtstrahlung der Wasserstoffelektronen. Ergänzende Betrachtungen über Bahnformen und Strahlungsfrequenzen" (3 parts) in Annalen der Physik, 82 (1927) 1017; 83 (1927) 903; 84 (1927) 880.