Bernard Ato IV

{{Short description|Viscount of Nîmes (died 1129)}}

{{ infobox nobility

| name = Bernard Ato IV, Viscount of Nimes

| image = Mariage of Ermengard of Carcassonne and Gausfred III of Roussillon.JPG|thumb|

| caption = Bernard Ato's daughter, Ermengard, standing between her mother and her father, is being betrothed to Gausfred III of Roussillon.

| 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

| birth_date =

| birth_place =

| death_date = 1129

| death_place =

| burial_place =

}}

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.{{sfn|Cheyette|2001|p=26}}

In 1096, Bernard joined the army of Raymond of Saint-Gilles to fight in the First Crusade.{{sfn|Riley-Smith|1997|p=166}} After returning from the Holy Land, Bernard retook Carcassonne in 1125.{{sfn|Cheyette|2001|p=142}}

He married Cecilia of Provence,{{sfn|Cheyette|2001|p=26}} daughter of the Bertrand II of Provence, and had:

• Bernard Ato V{{sfn|Cheyette|2001|p=26}}
• Roger I{{sfn|Cheyette|2001|p=26}}
• Raymond I Trencavel{{sfn|Cheyette|2001|p=26}}
• Ermengard married Gausfred III of Roussillon.{{sfn|Pegg|2008|p=1}}