NeVa (factory designation in Russia - 81-556 / 557/558, factory designation Škoda - 18Mt / 19Mt / 20Mt) is a type of electric subway car, structurally being a further development of the Škoda 6Mt experimental car. Cars of model 81-556 are motor head cars, 81-557 are motor intermediate cars, 81-558 are trailer intermediate cars. The name of the model comes from the name of the line to which these trains were supplied - Nevsko-Vasileostrovskaya, at the same time symbolizing the name of the St. Petersburg river of the same name.

The cars were developed by the St. Petersburg plant Vagonmash together with the Czech company Škoda Transportation s.r.o. (Pilsen, Czech Republic) by order of the St. Petersburg Metro and subsequently mass-produced for him by the Kirov Plant. In total, as of September 2020, 24 six-car trains have been produced: nine base models 81-556/557/558, eight modifications 81-556.1/557.1/558.1 and seven modifications 81-556.2/557.2/558.2. All of them entered the St. Petersburg Metro on the third line, where they are in regular operation.

In the subway, this train is a representative of a new, 4th generation, as it is equipped with asynchronous traction motors, which are started by power electronic converters made on IGBT devices, and also has an aluminum body and pneumatic spring suspension.