Coenzyme Q₁₀ (also known as ubiquinone, ubidecarenone, coenzyme Q, and abbreviated at times to CoQ₁₀ – pronounced like "ko-cue-ten" –, CoQ, Q10, or simply Q) is a 1,4-benzoquinone, where Q refers to the quinone chemical group, and 10 refers to the number of isoprenyl chemical subunits. This oil-soluble substance is present in most eukaryotic cells, primarily in the mitochondria. It is a component of the electron transport chain and participates in aerobic cellular respiration, generating energy in the form of ATP. Ninety-five percent of the human body’s energy is generated this way. Therefore, those organs with the highest energy requirements—such as the heart and the liver—have the highest CoQ₁₀ concentrations.

Idebenone (pronounced eye-deb-eh-known) is an organic compound of the quinone family and promoted commercially as a synthetic analog of coenzyme Q₁₀ (CoQ₁₀). Idebenone is claimed to have properties similar to CoQ₁₀ in its antioxidant properties. Idebenone is a synthetic analogue of coenzyme Q10 used in Europe in the treatment of vascular and degenerative diseases of the central nervous system.

Research on idebenone as a potential therapy of Alzheimer's disease have been inconsistent, but there may be a trend for a slight benefit. Idebenone may benefit those with Friedreich's ataxia.