Potamogeton alpinus is a species of aquatic plant known by the common names alpine pondweed and red pondweed. It is native to much of the Northern Hemisphere, including Eurasia, Greenland, Canada, and northern parts of the United States. It grows in water bodies such as ponds, lakes, marshes, and slow-moving streams. This is a perennial herb anchoring in the mud substrate via rhizome. It produces a cylindrical stem, sometimes with branches, approaching two meters in maximum length. It has lance-shaped leaves up to 8 cm long and 2 wide. The plant can be distinguished from other pondweeds by the red colour of its herbage. The inflorescence is a spike of flowers a few centimeters long rising above the water surface.