A cephalophore is a saint who is generally depicted carrying their own severed head. In Christian art, this was usually meant to signify that the subject in question had been martyred by beheading. Depicting the requisite halo in this circumstance offers a unique challenge for the artist: some put the halo where the head used to be, others have the saint carrying the halo along with the head, and some split the difference.
Associated legends often tell of the saint standing and carrying their own head after the beheading.