  We introduce a twisted quantum affine algebra associated to each simply laced
finite dimensional simple Lie algebra. This new algebra is a Hopf algebra with
a Drinfeld-type comultiplication. We obtain this algebra by considering its
vertex representation. The vertex representation quantizes the twisted vertex
operators of Lepowsky-Wilson and Frenkel-Lepowsky-Meurman. We also introduce a
twisted quantum loop algebra for the Kac-Moody case and give its level one
representation.
