The holotype and only known specimen of the pliosauroid plesiosaur Hauffiosaurus zanoni O'Keefe is a substantially complete and almost entirely articulated skeleton from the Toarcian Posidonien-Schiefer (Upper Lias, Lower Jurassic) of Holzmaden (Baden-Württemberg), Germany. The original description of this specimen was preliminary, and this paper presents a detailed re-description and revised diagnosis of the specimen, thus adding significant, new anatomical information. Characters such as the presence of a lateral palatal fenestra and the absence of a contact between the internal nares and the palatines are examples of phylogenetically relevant characters. The specimen presents a novel and unique combination of characters and body proportions, including a long ilium, short ischia, and propodials longer than any of their associated girdle bones, that separate it from all other pliosauroid taxa. Its elongate snout and long, slender teeth imply that this species most likely had a prey preference of fish.