Thorea hispida (Thore) Desvaux (Rhodophyta) was first found in Serbia in the river Danube at the end of the 19th century (as T. ramosissima Bory de Saint-Vincent). It was not found again in Serbia until it was reported in 1996 in the river Beli Timok, Danube basin. T. hispida (as T. ramosissima) is included in the Red List of rare and threatened algae in some European countries, and its habitats in Serbia are critically endangered. This paper reports this species in the river Sava, a tributary of the river Danube. Both monosporangia and carposporangia were observed. Compared with other European populations, the Serbian population varied in morphology, particularly in the reproductive structures.