Biostimulants are becoming an important tool in agriculture, helping to improve crop growth, resilience, and quality while supporting sustainable farming practices. These products, made from natural substances or microorganisms, enhance plants' natural processes. They can improve how plants use nutrients, handle stressful conditions like drought or salinity, and boost overall crop productivity and quality. The European Regulation (EU) 2019/1009 defines biostimulants as products “the function of which is to stimulate plant nutrition processes independently of the product's nutrient content with the sole aim of improving one or more of the following characteristics of the plant or the plant rhizosphere: (a) nutrient use efficiency; (b) tolerance to abiotic stress; (c) quality traits; or (d) availability of confined nutrients in the soil or rhizosphere”. This regulation has helped clarify what biostimulants are while encouraging their disciplined use in agriculture (EU 2019). Although biostimulants have shown great potential, there is still much to learn about how they work and how to maximise their benefits. Their effectiveness depends on crop type, dose, and timing, with a particular focus on crop responses under suboptimal conditions. Biostimulants have great potential to address cropping challenges such as climate change, resource scarcity, and the need for more sustainable farming methods. They offer a practical approach to increasing food production despite abiotic constraints. This Special Issue of Physiologia Plantarum “Biostimulants in Agriculture” includes seventeen studies that explore how biostimulants can help solve some of agriculture's biggest challenges. These studies investigate how biostimulants improve nutrient use efficiency, enhance plant stress tolerance, boost growth and increase quality traits. They also explore new formulations, like nanoparticles, and innovative concepts, such as glycostimulation, which uses various glycomolecules to enhance plant growth.