Carp, Cyprinus carpio L., is one of the most important cultured fish, especially in Central Europe and Asia (Kottelat & Freyhof 2007). In Europe, it is infected with a large number of parasites, many of them introduced from Asia, mainly from the Far East of Russia and China (Bauer, Musselius & Strelkov 1973; Hoole 1994; Kennedy 1994; Williams & Jones 1994; Hoole, Bucke, Burgess & Wellby 2001). Parasitic worms , i.e. helminths, are represented, among others, by tapeworms (Cestoda) including the most pathogenic species, the Asian fish tapeworm Bothriocephalus acheilognathi Yamaguti, 1934 (syn. B. gowkongensis Yeh, 1955), recently placed in the order Bothriocephalidea (Kuchta, Scholz & Bray 2008; Scholz, Kuchta & Williams 2011b). Other potentially pathogenic cestodes of carp belong to the order Caryophyllidea, the species of which possess a monozoic (only one set of genital organs) and unsegmented body and use tubificid oligochaetes as intermediate hosts (Mackiewicz 1972, 1994). At present, two caryophyllidean tapeworms parasitic in carp are of veterinary concern (Hoole et al. 2001; Oros, Hanzelova & Scholz 2004). Khawia sinensis Hsu, 1935 (Caryophyllidea: Lytocestidae), is native in East Asia and was described from the vicinity of Beijing in China (Hsu 1935). It successfully colonized a major part of Europe and was also imported to North America (Kulakovskaya 1961; Williams & Sutherland 1981). However, the veterinary importance of K. sinensis has decreased considerably during the last few decades, possibly as a result of the more recent introduction of Atractolytocestus huronensis Anthony, 1958 (Lytocestidae), to Europe (Oros, Hanzelova & Scholz 2009). Atractolytocestus huronensis was described from common carp in the USA (Great Lakes), but its North American origin is questionable because common carp are not native in this continent (Kohlmann, Gross, Murakaeva & Kersten 2003). Recently, the cestode has been introduced to a number of European countries, including Great Britain (Kralova-Hromadova, Stefka, Spakulova, Orosova, Bombarova, Hanzelova, Bazsalovicsova & Scholz 2010; Bazsalovicsova, Kral'ova-Hromadova, Stefka, Scholz, Hanzelova, Vavrova, Szemes & Kirk 2011). In this paper, another caryophyllidean cestode, Khawia japonensis (Yamaguti, 1934), which occurred originally in East Asia (Yamaguti 1934; Scholz, Shimazu, Olson & Nagasawa 2001), is reported from Europe for the first time. Journal of Fish Diseases 2011, 34, 943–949 doi:10.1111/j.1365-2761.2011.01311.x