What type of dragon is toothless from How to Train Your Dragon?

The answer is: Night Fury. The mysterious and deadly Night Fury turns out to be a big softy, for the most part, once Hiccup realizes dragons aren't mean — they're just cowards who won't stand up to the alpha.Toothless is among the last of the Night Furies, and gets his name from Hiccup as his teeth can retract on command.Source