Jens Jonas Schroeter Jansen (19 September 1900 – 26 October 1975) was a Norwegian archivist. He was born in Bærum as a son of vicar Jens Jonas Elstrand Jansen (1844–1912) and Jenny Therese Schroeter (1863–1942), and brother of Einar Jansen. In 1937 he married Hjørdis Sofie Berg. He finished his secondary education in 1918 and graduated from the Royal Frederick University with the cand.philol. degree in 1927 with a master's thesis on the Treaty of Björkö. In private relations, he used the very conservative pre-1907 orthography. He died in 1975.