Abstract: A helmet with adjustable rear hair support preferably includes a helmet portion, an adjustable chin strap, an adjustable head mechanism and an adjustable hair support. One end of the adjustable chin strap is sized to receive a chin and opposing ends of the chin strap are secured to opposing sides of an inside rim of the helmet portion. The adjustable head mechanism includes a left head strap, a right head strap, a head strap base and a head ratchet mechanism. Ends of the left and right head straps are secured to opposing sides of the inside rim of the helmet portion. The adjustable hair support preferably includes left and right pivot bases attached to the inside rim of the helmet portion. A hair support bar is pivotally engaged with the left and right pivot bases with left and right pivoting ratchet mechanisms.