| Bernard Ato IV, Viscount of Nimes | |
| Noble Family: | Trencavel |
| Father: | Raymond Bernard of Nîmes |
| Mother: | Ermengarde de Carcassonne |
| Spouse: | Cecilia of Provence |
| Issue: | Bernard Ato V Roger I Trencavel Raymond I Trencavel Ermengard |
| Death Date: | 1129 |
Bernard Ato IV (died 1129) was the Viscount of Nîmes of the Trencavel family from 1074 to his death. Bernard Ato was the son of Raymond Bernard of Nîmes (died 1074) and Ermengarde of Carcassonne.
In 1096, Bernard joined the army of Raymond of Saint-Gilles to fight in the First Crusade. After returning from the Holy Land, Bernard retook Carcassonne in 1125.
He married Cecilia of Provence, daughter of the Bertrand II of Provence, and had: