Potamogeton friesii Rupr. is reported for the first time from the Flora Iranica area. This species was collected from Chaharmahal va Bakhtiari, Gilan, Isfahan and Khuzestan provinces. It is distinguished from its closest relatives, Potamogeton pusillus and P. berchtoldii, by having 5-7-veind, wide leaf and stipules which split at the top and being free from each other at upper part and also this species is reddish or brownish in fresh status. A geographical distribution map, anatomical features and an illustration of the species are given.