The intrinsic and extrinsic factors (natural aging, diseases, infections, chemicals, radiation, heavy metals etc.) create oxidative stress, thereby causing reproductive defects in males and females. Similarly, oxidative stress causes the abnormalities in sperm and oocytes, and thus reduces the success of in vitro fertilization. Fungi and/or algae-derived metabolites (polysaccharides, carotenoids, ergothioneine, phycobiliproteins, phlorotannins, and cordycepin) alleviate the damages in ovaries and testis and correct the impaired reproductive functions (spermatogenesis, ovulation, fertilization and implantation) in the in vivo models by increasing antioxidant enzyme activities (superoxide dismutase, catalase, glutathione peroxidase etc.), making mitochondrial parameters better (membrane potential, distribution, dynamics and activity of mitochondria), decreasing oxidative stress (the reductions in intracellular ROS and malondialdehyde levels), inflammation (the reductions in COX-2, IL-6, IL-1β, and TNF-α levels) and apoptosis (the reductions in