Selenium (Se) is an essential micronutrient for animals, playing a critical role in antioxidant defense, thyroid function, and immune system support. However, its deficiency in forage crops is prevalent in many agricultural regions, affecting both animal and human health. The Se enrichment in forage crops has garnered increasing attention as a sustainable method for improving Se intake in grazing livestock. This chapter explores the role of Se in forage crop production, including its uptake, bioavailability, and potential for biofortification. Various methods of enhancing Se concentration in forages have been discussed, including soil fertilization, foliar application, and the use of Se-enriched fertilizers. The effectiveness of different Se forms, such as selenate and selenite, as well as the role of plant species in Se accumulation, has been objectively examined. Additionally, key challenges related to the environmental impact of Se application, its potential toxicity to plants and animals, and the implications for pasture management have also addressed. Moreover, future research directions have proposed, focusing on optimizing Se utilization in forage systems to ensure sustainable and safe supplementation for livestock and humans consuming animal products.