Ermesinde of Carcassonne (972–1057) was a noblewoman in southern France, the daughter of Roger I of Carcassonne. She married to Ramon Borrell, Count of Barcelona.
While he lived she was politically active and presided over assemblies and tribunals. After his death in 1018 she became regent for her son Berenguer Ramon I until 1023. After this, she continued to wield power. In contrast to her son, she favored war with the Muslim powers to the South, partly because of the discontent of the nobles at his police of peace. When he died in 1035, she became regent for her grandson until he was declared to be of age in 1044.