Human coenzyme Q (CoQ10) or ubiquinone is mainly known for its bioenergetic role as a proton and electron carrier in the inner mitochondrial membrane and is also an endogenous lipophilic antioxidant, ubiquitous in biological membranes. It is also present in plasma lipoproteins, where it plays a well-recognized antioxidant role. More recently coenzyme Q10 was also shown to affect gene expression by modulating the intracellular redox status. Its involvement in many cellular and extracellular functions suggests that its use as a food supplement could be beneficial in conditions associated with increased oxidative stress underlying different pathological conditions. In reproductive biology, CoQ10 has been shown to play a role in fertility of both males and females.