The genusFlavivirus, familyFlaviviridae, includes a number of important arthropod-transmitted human pathogens such as dengue viruses, West Nile virus, Japanese encephalitis virus and yellow fever virus. In addition, the genus includes flaviviruses without a known vertebrate reservoir, which have been detected only in insects, particularly in mosquitoes, such as cell fusing agent virus, Kamiti River virus,Culexflavivirus,Aedesflavivirus, Quang Binh virus, Nakiwogo virus and Calbertado virus. Reports of the detection of these viruses with no recognized pathogenic role in humans are increasing in mosquitoes collected around the world, particularly in those sampled in entomological surveys targeting pathogenic flaviviruses. The presence of six potential flaviviruses, detected from independent European arbovirus surveys undertaken in the Czech Republic, Italy,Portugal, Spain and the UK between 2007 and 2010, is reported in this work. Whilst theAedesflaviviruses, detected in Italy fromAedes albopictusmosquitoes, had already been isolated in Japan, the remaining five viruses have not been reported previously: one was detected in Italy, Portugal and Spain fromAedesmosquitoes (particularly fromAedes caspius), one in Portugal and Spain fromCulex theilerimosquitoes, one in the Czech Republic and Italy fromAedes vexans, one in the Czech Republic fromAedes vexansand the last in the UK fromAedes cinereus. Phylogenetic analysis confirmed the close relationship of these putative viruses to other insect-only flaviviruses.