Mechanical oscillator (10) comprising an inertial body (101) joined to a support (100) by means of an elastic system (102, 103, 104, 105, 106, 107) arranged to provide the inertial body (101) with substantially no degrees of freedom in translation and with substantially two degrees of freedom in rotation about a point being substantially fixed with respect to said support (100). Said elastic system comprises at least two rods (102, 103, 104) situated in a single plane when the inertial body (101) is in a neutral position.