Eleven species of the genus Cyperus have been reported from Hungary so far, of which 3 are certainly aliens. A small population of C. odoratus, new for the flora of Hungary, was found along the River Danube near Foktő settlement (Bács-Kiskun County, S Hungary) in late autumn of 2019. On this occasion blooming specimens were observed in the floodplain ruderal vegetation on the bank of a fork of the Danube. This species is widespread in the tropical and subtropical regions of the World, and was first introduced to Europe in the early 1950s.  More recently it has been spreading along certain rivers of Italy and Spain. It was discovered along the river Danube in Romania in the early 1990s, and later at the upper parts of the river in Bulgaria, Croatia and Serbia. Its introduction into Hungary is connected with the Danube, too. Based on foreign experience, it is probable that C. odoratus will be spreading along the Hungarian Danube system, hopefully, not as an invasive species.