Einar Jansen (27 March 1893 – 13 December 1960) was a Norwegian historian, genealogist and archivist.
He was born in Røyken as the son of priest Jens Jonas Jansen (1844–1912) and Jenny Therese Schroeter (1863–1942).
The family soon moved to Sandvika, and after finishing his secondary education in 1911, he enrolled in philology at the University of Kristiania, graduating with the cand.philol.
His final paper, Det suspensive lovvetos anvendelse i norsk konstitusjonel praksis, mixed history and constitutional law.
He began working there in 1924, and soon became editor-in-chief, as the three editors-in-chief Anders Krogvig, Gerhard Gran and Edvard Bull, Sr. died in 1924, 1925 and 1932 respectively.