Procambarus machardyi, a new crayfish of the gracilis group of subgenus Girardiella, is described from an intermittent stream in Caddo Parish, Louisiana. It is similar to P. kensleyi Hobbs, 1990 but differs in having the rostrum distinctly shouldered before acumen and form I male pleopod with lamellate crest of caudal element extending caudally distinctly beyond mesial process in mesial view, longer cephalic process, and central projection widely separated from the crest of the caudal element. It differs from P. curdi Reimer, 1975 in having a more strongly developed caudal knob, a shorter central projection more widely separated from the crest of the caudal element and directed distally, not caudolaterally, and wider areola. Procambarus parasimulans Hobbs & Robison, 1982 has a narrower caudal crest like that of P. kensleyi and P. curdi but has the other terminal elements generally similar to P. machardyi.