Rapid global population growth intensifies pressure on agriculture to meet food demand sustainably, necessitating the adoption of data-driven precision agriculture (PA) methods. An unmanned aerial system (UAS) is increasingly favoured in PA due to their adaptability, cost-effectiveness and high-resolution imaging capabilities. This chapter provides an overview of UAS applications in PA, emphasizing their capability to gather precise and high spatial-temporal resolution data for crop monitoring, weed and pest identification, nutrient and water management and yield estimation. The chapter explores diverse imaging sensors suitable for UAS integration, including RGB, multispectral, hyperspectral, thermal infrared cameras and LiDAR imagers. The chapter also provides insights into geometric and radiometric calibration processes and data analysis techniques. Challenges and future trends in UAS research for PA are addressed, underlining their potential to transform farming practices. Overall, the chapter provides a comprehensive overview of current research and development and the transformative role of UAS in PA.