"Your hair is on fire!"

Translation: Deine Haare brennen!

[dbayly]

a more literal (=better) translation is surely "Dein Haar steht in Flammen".

Deine Haare brennen is closer to "your hair is burning'

[onecrane]

For my fellow native English speakers who may be perplexed by what literally translates to the wrong-sounding "Your hairs are on fire," apparently German common practice is indeed to use the plural when referring collectively to one's hair: https://en.m.wiktionary.org/wiki/Haar

[Max.Em]

Dein Haar brennt works as well. Sounds a bit more fancy....