Microwave absorber comprising various agricultural residue-based microwave-absorbing materials is one of the interesting and challenging topics to modern-day scientists and engineers. In this work, we explicitly present an overview of the microwave absorption mechanism, different measurement techniques, various types of microwave absorber structure, and factors affecting the microwave absorption. We also discuss various stages of fabrication of lightweight and low-cost microwave absorber using different types of agricultural residues. This review provides an overall summary of the state-of-the-art progress on various agricultural residue-based microwave absorbers. Finally, some new prospects are also discussed from the existed theoretical and experimental results in this work, to propel their application in practice.