Activated carbon (AC) is a porous carbonaceous material with distinct physical and chemical properties that has widespread use in a variety of applications. In recent years, AC has been explored and has become more popular as a catalyst or catalyst support in various reactions. The surface area, porosity, and surface chemistry of ACs are appropriate for consideration in catalysis applications. The procedures used in the synthesis of AC, such as precursor selection, carbonization, and physical or chemical activation, have a direct impact on the properties of the resulting AC. The properties can be enhanced with surface modifications to improve its catalytic activity. This work covers the recent use of AC as the catalyst in several reactions, as well as methods investigated to improve the AC properties for catalytic performance. This chapter could serve as a guideline for understanding the properties and application of AC-based catalysts.