Per Karl Hjalmar Dusén (1855–1926) was a Swedish civil engineer, botanist and explorer.

As a botanist his interests included pteridology, bryology, and paleobotany.

He made botanical expeditions to Africa, Greenland, and South America.

During his expeditions to Greenland, he visited Disko Island to catalogue the variety of flowering plants, horsetails and ferns.

Later, these fossils were studied by the German paleobotanist Paul J. Menzel (1864–1927).