<p>Selenium is an essential trace mineral that has a central role to play in reproductive health through the provision of antioxidant defence, regulating hormone production as well as preserving gamete integrity. Clinical application is, however, hampered by a low therapeutic window that at low levels as well as high levels can cause reproductive dysfunction. The classical inorganic and organic selenium supplements tend to show low levels of bioavailability and demonstrate elevated toxicity levels, which require the elaboration of safer and more effective ones. With custom advantages like greater biocompatibility, less systemic toxicity and enhanced bioavailability, selenium nanoparticles (SeNPs) have become a potential application in reproductive medicine. The review gives a clear picture of the methods of SeNP synthesis such as chemical and green/biological, and sheds some light on the interrelationship between physicochemical properties of SeNPs and their biological performance. The mechanistic applications of SeNPs in the field of reproductive biology are outlined, especially in the perspective of the antioxidant and endocrine modulatory effects and selective targeting of the reproductive organs. In vitro and in vivo studies prove that SeNPs have potential to enhance sperm quality and testicular functionality; ovarian growth; and embryo survival in several species. They can also be used in assisted reproductive technologies (ART), including sperm cryopreservation and embryo culture systems, increasing their translational value. However, clinical implementation is still constrained by existing gaps in human studies, regulatory issues and standardized, scalable manufacturing procedures.</p>