The mosquito known in the northern hemisphere as Culex pipiens (a.k.a. Culex pipiens pipiens or Culex pipiens form pipiens) is not known from Australia. However, there are four species of the Culex pipiens group: two indigenous, Culex australicus and Culex globocoxitus, and two introduced, Culex quinquefasciatus and what is known locally as Culex molestus (?  =  Culex pipiens molestus or Culex pipiens form molestus), all four being members of the pipiens subgroup ( =  ‘pipiens complex’). The species status of the indigenous Cx. australicus and Cx. globocoxitus in Australia appears to be accepted as legitimate; however, the true identity of the mosquito called ‘Cx. molestus’ in Australia remains contentious, even as its local profile has been increasing over the past 40 years. This paper provides an overview of the taxonomic and biologic knowledge of these species, and their public health significance as vectors of arboviruses in Australia.