Diphasiastrum alpinum, alpine clubmoss, is a species of clubmoss. It was first described by Carl Linnaeus in his Flora Lapponica, 1737, from specimens obtained in Finland.
It has a circumpolar distribution across much of the northern parts of the Northern Hemisphere: much of Canada, the northwestern United States, northern and central Europe, Russia, China and Japan. It is an indicator of alpine tundra and boreal climates. It is found in mountains and moors often with Calluna and grasses.
Diphasiastrum alpinum grows 10 to 20 cm (4 to 8 in) tall from stems which grow just under the surface of the ground. The leaves are hollow at the bases. The female stems produce strobili up to 3 cm (1 in)long.
Diphasiastrum alpinum may hybridize with Diphasiastrum sitchense.