Installation for seawater desalination by multiple effect distillation with thermal vapour compression intended for coupling with a thermal power plant, comprising a series of distillation cells (A, B, C, D, E, F), each cell (effect) consisting of • a closed vessel comprising at least one means for making the seawater flow as a thin film over a heat exchanger heated by the steam to a sufficient temperature to vaporize a portion of the seawater flowing under gravity as a thin film over the heat exchanger, • a means for conveying the steam thus formed to the heat exchanger of the next effect, • a means for removing liquid distilled water formed by condensation of the steam in the heat exchangers, • a means for sucking the noncondensable gases (O 2, N 2, CO 2), • a means for removing the brine remaining after evaporation of a portion of the seawater, each effect operating at a lower temperature and pressure than those of the previous effect, and a vapour compression means for compressing at least a portion of the water vapour issuing from one of the effects (offtake effect), preferably the last, and for recycling it to the first effect, this installation being characterized in that the vapour compression means comprises both a mechanical vapour compressor operating exclusively with electricity and a steam jet ejector operating exclusively with motive vapour supplied by the thermal power plant at the turbine exit, the two compressors (6, 9) being mounted in parallel between their offtake effect and the first effect and operating alternately according to the quantity of steam available at the turbine exit, and in that the installation further comprises, in combination, (a) a heat removal means located in the last effect, (b) a first heat recovery means located in the distilled water removal pipe and (c) a second heat recovery means located in the brine removal pipe, each of these three means (a), (b) and (c) operating independently of one another. a series of distillation cells (A, B, C, D, E, F), each cell (effect) consisting of • a closed vessel comprising at least one means for making the seawater flow as a thin film over a heat exchanger heated by the steam to a sufficient temperature to vaporize a portion of the seawater flowing under gravity as a thin film over the heat exchanger, • a means for conveying the steam thus formed to the heat exchanger of the next effect, • a means for removing liquid distilled water formed by condensation of the steam in the heat exchangers, • a means for sucking the noncondensable gases (O 2, N 2, CO 2), • a means for removing the brine remaining after evaporation of a portion of the seawater, each effect operating at a lower temperature and pressure than those of the previous effect, and • a closed vessel comprising at least one means for making the seawater flow as a thin film over a heat exchanger heated by the steam to a sufficient temperature to vaporize a portion of the seawater flowing under gravity as a thin film over the heat exchanger, • a means for conveying the steam thus formed to the heat exchanger of the next effect, • a means for removing liquid distilled water formed by condensation of the steam in the heat exchangers, • a means for sucking the noncondensable gases (O 2, N 2, CO 2), • a means for removing the brine remaining after evaporation of a portion of the seawater, a vapour compression means for compressing at least a portion of the water vapour issuing from one of the effects (offtake effect), preferably the last, and for recycling it to the first effect, (a) a heat removal means located in the last effect, (b) a first heat recovery means located in the distilled water removal pipe and (c) a second heat recovery means located in the brine removal pipe,