Karditsa (Greek: Περιφερειακή ενότητα Καρδίτσας) is one of the regional units of Greece. It is part of the region of Thessaly.
Karditsa borders the regional units of Trikala to the north, Larissa to the east, Phthiotis to the southeast, Evrytania to the south, Aetolia-Acarnania to the southwest and Arta to the west. The main rivers are Megdovas in the south, the Pineios in the north, and the Enipeas in the east. The Plastiras Dam and Lake Plastiras, located to the west of the city of Karditsa, supply water to the plains and the central part of Greece.
Located in south-western Thessaly, it is primarily an agricultural area. Farmlands dominate the central and the eastern part, which belongs to the Thessalian Plain. The western and southern part of the regional unit is mountainous, notably the Pindus mountains. The Agrafa region, straddling the border with Evrytania, is well known for its resistance against Ottoman rule and its harsh landscape.