The mechanical oscillator according to the invention comprises an oscillating body (601), at least one rigid intermediate body (602) and a support (600). Each rigid intermediate body is connected to the support by a pair of elements (610, 611) providing rotational guidance. The elements of each pair are elastically substantially identical to each other and extend along respective axes which, in orthogonal projection onto a plane parallel to the oscillation plane of the oscillating body, cross at a point (G) and are symmetric to each other with respect to a line (x) passing between the points of junction of the first pair of elements to the rigid intermediate body. The rigid intermediate body is connected to the oscillating body by at least one further element (604, 605) providing relative guided mobility between the oscillating body and the rigid intermediate body in a direction substantially parallel to the line (x) during regular functioning of the mechanical oscillator. In a variant the pair of elements connect the rigid intermediate body to the oscillating body and the at least one first further element connects the rigid intermediate body to the support.