Herman Didrich Janson (8 July 1757 – 13 March 1822) was a Norwegian shipper, businessman and powerful figure, and owner of Damsgård hovedgård, which he bought at auction in 1796. The gardens were often known as the Janson-gården and as the Jansonmarken. The property was in the family's ownership until 1983.[1]
Herman Didrich Janson was also the owner of Stiftsgården from 1805, an estate which he sold in 1809 to his stepson, County Governor Edvard Hagerup.