Abstract: The rate gyro according to the invention comprises, in one optical block, three optical cavities (B, C, D) of square shape which are devised in such a way that each of the corners of a cavity (B, C, D) coincides and communicates with the corner of another cavity, a control mirror (M.sub.4 to M.sub.6) or reading mirror (M.sub.1 to M.sub.3) being associated with each pair of coincident corners, the three cavities (B, C, D) communicating with a cathode chamber (CK) by way of three cathode capillaries (CK.sub.1 to CK.sub.3) with an equilibration chamber (CE) by way of three equilibration capillaries (CE.sub.1 to CE.sub.3). The control mirrors (M.sub.4 to M.sub.6), the reading mirrors (M.sub.1 to M.sub.3), the cathode capillaries (CK.sub.1 to CK.sub.3), the equilibration capillaries (CE.sub.1 to CE.sub.3) and the anodes are mutually symmetric according to a symmetry of revolution of order 3 about the activation axis .DELTA. (that is to say may be deduced from one another by a 120.degree. rotation about the axis .