Bernard Ato V (died 1163) was the Viscount of Nîmes of the Trencavel family from 1129 to his death.
In 1138, Bernard Ato swore an oath of fidelity to Alfonso Jordan, Count of Toulouse, along with his brothers Roger of Carcassonne and Raymond of Béziers. Nevertheless, because his father Bernard Ato I had supported William IX of Aquitaine in his attempt to take Toulouse and because his lands controlled the roads between Alfonso's Languedocian and Provençal lands, Bernard Ato and Alfonso were fundamentally at odds. Alfonso even seized some castles in the vicinity of Nîmes itself.