Otto Delphin Amundsen (1896 – 1957) was a Norwegian genealogist.
He was born in Kristiania. He was an engineer by profession, but is best known for working on the history of indivuduals and families. He issued ahnentafels of the families Arentz, Astrup, Bay, Lange and Wiese, as well as a book of biographies about laureates of the Order of St. Olav; Den kongelige norske Sankt Olavs Orden 1847–1947 for the Order's 100th anniversary in 1947. He has also edited the book of student biographies from the Norwegian Institute of Technology; Vi fra NTH.[1]