Northern marsh orchid can be recognised by its lip marked with dark spots and lines that do not usually form loops, as well as by its vivid purple-violet flower colour.
Northern marsh orchid occurs throughout the northwestern part of Europe. It is found in southwestern Norway, southern Sweden, Denmark (including the Faroe Islands) and the UK. In the UK it is widespread in northern England, Northern Ireland, Scotland (including the Shetland Islands) and Wales. It is found at up to 600 m above sea level. Damp or wet habitats with calcareous, neutral or slightly acid soils, such as marshy fields, road verges, lake margins, fens, marshes, flushes, coastal cliffs, dune slacks, and sometimes peat bogs and open woodland.