Jonzac (French pronunciation: [ʒɔ̃zak] ⓘ; Poitevin-Saintongese: Jhonzat) is a commune of the Charente-Maritime department, Nouvelle-Aquitaine, southwestern France.

The river Seugne flows northwest through the commune and crosses the town.

Jonzac is located in the south of Charente-Maritime, with the department's capital La Rochelle 105 km to the northwest.

The capital of the Nouvelle-Aquitaine region, Bordeaux, is 90 km to the southwest.

55 km to its east is Angoulême, capital of the neighbouring Charente department.