The electro-optic phase modulator, intended to modulate the optical phase of an incident lightwave, includes an electro-optic substrate with an entrance face and an exit face; an optical waveguide extending between a guide entrance end located on the entrance face and a guide exit end located on the exit face, the incident lightwave being partially coupled in the waveguide into a guided lightwave propagating in an optically guided manner along the optical path of the waveguide between the entrance end and the exit end; at least two electrodes arranged at least partially along the waveguide, parallel to and on either side of the latter, defining between each other an inter-electrode gap, which allow to introduce, when a modulation voltage is applied between them, a modulation phase-shift, function of the modulation voltage, on the guided lightwave. The waveguide has one first curved guide portion between the entrance end and the electrodes.