Abstract: A connecting device for connecting two mechanical parts includes a rod having a section between a stop and a threaded portion. The rod is inserted into the parts, and a nut is screwed onto the threaded portion in order to hold the parts between the stop and the nut. An anti-rotation system blocks rotation of the nut and includes a washer interacting with the rod to be constrained to rotate with it. The washer has two protuberances, each engaged in a notch of shape complementary to the rod. The anti-rotation system has a ring with an inner periphery of with a shape complementary to that of an outer periphery of the nut in order to be secured to the nut. The ring is secured to the washer by a screw.