Some tropical Ludwigia species have been planted as ornamentals in Hungarian thermal springs since the 1920s. Although they have become naturalised or even invasive in a few places, their specific identity remained generally uncertain. Our herbarium and field studies revealed that three species of alien water-primroses occur in Hungary. The most frequently planted one is Ludwigia repens, which is, however, a sporadic species in its native distribution area. We have found this species in several parts of the country. Although a few escaped and self-sustaining populations were also observed, this species has appeared to be non-invasive so far. Ludwigia grandiflora appeared in Hungary at the beginning of the 2000s. At the moment it is known from three localities, though spreading rapidly, becoming already invasive in its locality at Tata city. A similar species, L. peploides has recently been reported from two localities, where it forms small stands; the success of its naturalisation can be assessed in the future. We found no evidence for the Hungarian occurrence of L. alterniflora that had been published from Eger city. Therefore we suggest deleting this species from the current Hungarian checklist.