Cosmetic product application device, related kit and reservoir The device (14) includes: —an applicator (40), comprising a gripping member (44) and a product application member t (46) intended to plunge into a reservoir (12) of a cosmetic product; —an intermediate part (42) comprising a attachment sleeve (70) for the removable fastening of the gripping member (44), with the attachment sleeve (70) defining a circulation hole (76) of the product application member (46). The intermediate part (42) comprises an outer band (72) for protecting the applicator (40) protruding opposite the attachment sleeve (70), the band (72) having at its free edge (88) an insertion opening (90) of the reservoir (12). The intermediate part (42) comprises an inner fastening member (74) for the removable fastening of the reservoir (12), protruding in the band (72) opposite the attachment sleeve (70).