A timepiece oscillator including a resonator formed by a tuning fork which includes at least two mobile oscillating parts, fixed to a connection element by flexible elements whose geometry determines a virtual pivot axis having a determined position with respect to this connection element and around which the respective mobile part oscillates, and the center of mass of the mobile part coincides in the rest position with the respective virtual pivot axis, and, for at least one of the two mobile parts the flexible elements are formed of intersecting resilient strips extending at a distance from each other in two parallel planes, and whose directions, in projection on one of the parallel planes, intersect at the virtual pivot axis of the mobile part.