A piezoelectric resonator for a rotary piezoelectric motor, the resonator comprising a stationary base and an oscillating mass extending about a longitudinal axis, the oscillating mass being provided with at least one inertia-block, preferably two opposing inertia blocks, wherein the resonator comprises a flexible blade guide connecting the oscillating mass to the base, so that the oscillating mass can be oscillated about a centre of rotation in a pendulum movement, the flexible guide comprising at least one first flexible blade connected to the base and/or to the oscillating mass to allow the displacement of the oscillating mass relative to the base, the flexible blade guide comprising a spiral spring connected to the base and/or to the oscillating mass, the spiral spring including at least partially an electrically actuatable piezoelectric material to deform the spiral spring and oscillate the oscillating mass.