Optical sensing technologies have revolutionized agriculture by enabling precision farming practices that optimize resource use and enhance crop productivity. This chapter provides an overview of optical sensing, its definition, historical development, fundamental principles, various sensing technologies, and applications. Optical sensing plays a crucial role in monitoring crop health, soil properties, water quality, weeds, and pests, and predicting yields. However, it faces challenges like environmental factors, calibration, and integration issues. The chapter emphasizes the continued significance of optical sensing in sustainable agriculture and its potential role in shaping future farming practices. As technology develops and becomes more affordable, optical sensing is poised to play an increasingly important role in precision agriculture.