Selenium (Se) is a vital micronutrient crucial for the health of both humans and animals, significantly contributing to antioxidant defence, immune function, and thyroid metabolism. However, its role in plant growth and enhancement remains a topic of ongoing debate. The current low concentrations of Se in staple crops (less than 100 mg Se kg⁻1) underscore the urgent need for genetic improvement strategies to increase Se accumulation. The selenium use efficiency (SeUE) differs widely among plant species and genotypes, largely due to genetic differences that influence selenium uptake, translocation, and metabolism. Quantitative trait loci (QTL) mapping is a key genetic strategy that connects specific genomic regions to observable traits. Identifying QTL related to SeUE is crucial for breeding programs focused on developing crops with higher selenium content while also addressing potential toxicity issues. This chapter offers a detailed overview of QTL mapping techniques for SeUE and highlights their importance in biofortification efforts aimed at enhancing dietary selenium intake and improving crop resilience to environmental challenges.