An apparatus for treating used absorbent sanitary products, comprising:- a rotary cylindrical autoclave (14) having a side wall (42) and two ends, at least one of which terminates in a hatch (18, 20) that can be opened to enable access to said autoclave (14) and sealably closed to enable pressurization of said autoclave (14);- a circuit for heating and pressurizing the autoclave (14) for heating the absorbent sanitary products to a sterilization temperature; and- a plurality of cutting nozzles (38) supplied by pressurized fluid, which are arranged for directing respective jets of pressurized fluid inside said autoclave (14).