Christian Erasmus Otterstrøm (Otterström) Jensen (1859–1941) was a Danish pharmacist and botanist, for decades a leading bryologist in Scandinavia. He studied botany and pharmaceutics at the University of Copenhagen and the Pharmaceutical College in Copenhagen. For the better part of his adult life, he ran a pharmacy in Hvalsø, Denmark, while devoting all available time to the study of mosses.