Abstract: Acoustic positioning device for a vessel comprising N transponders (B.sub.1 . . . B.sub.i . . . B.sub.N).A fixed acoustic transmitting means (E) periodically transmits acoustic pulses at frequency f. The responses of the transponders (B.sub.1 . . . B.sub.i . . . B.sub.N) are received by the acoustic array (A.sub.1, A.sub.2) of the vessels. The time origins are transmitted by a radio antenna to the surface vessel. In the case of submarines, two stable clocks are used, one of which is on board the submarine. Processing circuits make it possible to know the position of submarines.Application to the positioning of vessels in an oil production field or for oceanographic research.