Red yeast rice, sometimes called red fermented rice, red kojic rice, red koji rice, or ang-kak, is a bright reddish purple fermented rice. It acquires its colour from being cultivated with the yeast Monascus purpureus.

Red yeast rice is sold in jars in Asian markets as a pasteurized wet aggregate, whole dried grains, or as a ground powder. It was a commonly used red food coloring in East Asian and Chinese cuisine prior to the discovery of chemical food coloring. It has also been used in Chinese herbal medicine.

A new study revives a running controversy about its purported cholesterol-lowering effects on the body. In the United States and Europe, red yeast rice has been proposed as an alternative cholesterol-lowering treatment for people who cannot take statins because of severe side effects, mainly muscle wasting and weakness.

But, even though it is seen as an alternative, it has also some complications and potential risks.