NAD or Nad may refer to:
In geography:

• Nad, County Cork, a village in Ireland
• North American Datum, a series of geographic coordinate systems
• North Atlantic Drift, an Atlantic ocean current
• Hobli a subdivision of a taluka in southern India

Nicotinamide adenine dinucleotide (NAD) is a coenzyme found in all living cells. The compound is a dinucleotide, because it consists of two nucleotides joined through their phosphate groups. One nucleotide contains an adenine base and the other nicotinamide. Nicotinamide adenine dinucleotide exists in two forms, an oxidized and reduced form abbreviated as NAD and NADH respectively.