Diffuse reflectance spectroscopy is a method that has been successfully used to estimate soil organic carbon, organic matter, and numerous other properties related to soil health. In this chapter, we introduce the concept of soil health and the need for sensor-based soil health measurements. We then review methods of soil spectroscopy, including instrumentation and modeling methods for both laboratory and in-situ sensing. The ability of spectroscopy to estimate key soil health properties is covered along with the potential advantages of merging other sensor data with spectral data. The chapter concludes with a case-study example, an exploration of future trends, and suggested sources of additional information.