Niacinamide or nicotinamide is a form of vitamin B₃ found in food and used as a dietary supplement and medication. As a supplement, it is used by mouth to prevent and treat pellagra (niacin deficiency). While nicotinic acid (niacin) may be used for this purpose, niacinamide has the benefit of not causing skin flushing. As a cream, it is used to treat acne. It is a water-soluble vitamin. Niacinamide is the supplement name while nicotinamide is the scientific name.

Side effects are minimal. At high doses liver problems may occur. Normal amounts are safe for use during pregnancy. Niacinamide is in the vitamin B family of medications, specifically the vitamin B₃ complex. It is an amide of nicotinic acid. Foods that contain niacinamide include yeast, meat, milk, and green vegetables.

Niacinamide was discovered between 1935 and 1937. It is on the World Health Organization's List of Essential Medicines. Niacinamide is available as a generic medication and over the counter. Commercially, niacinamide is made from either nicotinic acid (niacin) or nicotinonitrile. In some countries grains have niacinamide added to them.