Nr I is a class of articulated six-axle (B′2′B′ wheel arrangement), chopper-driven tram operated by Helsinki City Transport on the Helsinki tram network. All trams of this type were built by the Finnish metal industry corporation Valmet between the years 1973 and 1975.Between 1993 and 2004 all trams in the class were modernised by HKL and redesignated as Nr I+ class. Currently HKL classifies them as NRV I.