Mosaic disease of eggplant (Solanum melongena L.) is common in many fields of southern Iran. A virus isolated from diseased plants in the Boushehr Province was characterised by biological, serological, physiochemical and molecular studies. The virus was mechanically transmissible to Nicotiana tabacum cv. Turkish and several other solanaceous species and to Chenopodium amaranticolor and C. quinoa. Purified preparations of the virus contained flexuous rod-shaped particles. Two aphid species, Myzus persicae and Aphis gossypii, transmitted the virus between Turkish tobacco plants. An antiserum raised against purified virus preparation was used in the detection of the virus. Molecular weights of the virus genome and the coat protein (CP) were estimated at 3.1–3.2 × 10⁶ and 36 × 10³ Da, respectively. The 3′ region of the virus genome, including the CP and the untranslated region (UTR), was amplified using two pairs of general primers of the family Potyviridae. Sequence information identified the virus as a strain of Potato virus Y (PVY), designated eggplant strain of PVY (PVY-Eg), with the highest sequence homology to a tomato strain of PVY (PVY-LY84.2) from Spain, and a somewhat lower homology to an Indian isolate of Eggplant mottle virus belonging to the PVY^O subgroup. Cluster dendrograms based on CP amino acid and 3′-UTR sequences placed PVY-Eg within the PVY^NP subgroup. This is the first report on the characterisation of a PVY^NP strain infecting eggplant in Iran.