Rarh region (Bengali: রাঢ়) of West Bengal is the historic name for a large area that lies at the transition between the Chhotanagpur plateau and the Ganges Delta. Western parts of Rarh merging with Chhotanagpur plateau was historically called Vajjabhumi. Parts of the districts Murshidabad, Birbhum, Bankura, Bardhaman, Hooghly, Howrah, Medinipur and Nadia contributes to the rarh region.

Eastern Rarh: Western Mushidabad, northern part of Birbhum, eastern Burdwan,the whole of Hooghly, the whole of Howrah, eastern Midnapur, and a part of of Bankura district.

Western Rarh consists of Santhal Pargana, most part of Birbum, western Burdwan, Bankura district, Kasmar, Peterwad, Gola, Jeredi, Ramgarh of Hazaribag (now Giridih) district, Silli, Sonahatu, Bundu and the Tamar Police Station of Ranchi district, Singhbhum district, Jhargram Subdivision and Sadar North and Sadar South Subdivision of Midnapur district.'

The region is about 50 to 100 m above the sea level.

The word Rarh originated in the ancient Austric language and means 'a land of red soil'. The Chinese called it 'Lati', the Greek called it 'Ganga Ridi' (Greek: Γάγγᾱ Ῥύδη, from Ῥύδην: flowingly), the Aryans called it 'Rattha.'