There is more than one artist with this name.
1) Nightmare, a French heavy metal band.
2) Nightmare, a Japanese hardcore punk band.
3) Nightmare, an Italian progressive metal band.
4) Nightmare, a Serbian rapper.
5) Nightmare, a Polish thrash/speed metal band.
6) Nightmare, a Croatian rapper
For the Japanese visual rock band Naitomea, see ナイトメア.
1) Nightmare is a heavy metal band from Grenoble, France, formed in 1979 and stopped in 1987 then came back in 1999 with Jo Amore (ex drummer) at the microphone