A number of European species of the genus Arrenurus (Acari, Hydrachnellae) are revised. The following synonyms are established: A. hofsteni Walter and A. sinuator commutatus Viets as junior synonyms of A. latus Barrois & Moniez; A. ornatulus Viets of A. compactus Piersig; A. walteri Koenike of A. neumani Piersig; A. cyanipes (Lucas) sensu Walter and A. bucharicus Sokolow of A. papillator (Müller); A. stjoerdalensis naias Lundblad of A. coronator Thor; A. eugeminus Piersig and A. imitator Koenike of A. geminus George; A. insperatus George of A. stjoerdalensis Thor; Arrenurus brachyurus Viets of A. bifidicodulus Piersig and Arrenurus truncatellus georgei Piersig of A. truncatellus (Müller). A. spatiosus Viets has been raised to species rank, while A. papillator bicolor Viets should stand as a subspecies. A. distans Walter, A. scourfieldi Soar and A. tubulator (Müller) are considered good species. A. bueranus Münchberg, A. curtus George, A. incertus Biesiadka, A. soari George and A. paluster Thor are considered species incertae. A lectotype has been designated for A. scourfieldi. Finally, a small number of old identifications have been re-examined.