This paper provides a comprehensive review of drought indices, which are essential tools for characterizing drought and facilitating drought management. Drought is a stochastic natural hazard characterized by intense and persistent precipitation deficits, leading to significant impacts on agriculture and hydrology. The review highlights the unique features of drought, including delayed effects and dynamic dimensions such as severity and duration, which make it challenging to characterize. Over 100 drought indices have been proposed, with some being operationally used to characterize drought at regional and national levels. These indices cover different types of drought, including meteorological, agricultural, and hydrological drought. By quantifying severity levels and indicating the start and end of drought, these indices aid in various operations such as early warning, monitoring, and contingency planning. The paper discusses the development of drought indices, their performance, and the trend in their evolution. It also emphasizes the importance of combining indices to provide a more comprehensive characterization of drought events. The review concludes by highlighting the need for a universal definition and standardized methods to address the variability in drought types and applications.This paper provides a comprehensive review of drought indices, which are essential tools for characterizing drought and facilitating drought management. Drought is a stochastic natural hazard characterized by intense and persistent precipitation deficits, leading to significant impacts on agriculture and hydrology. The review highlights the unique features of drought, including delayed effects and dynamic dimensions such as severity and duration, which make it challenging to characterize. Over 100 drought indices have been proposed, with some being operationally used to characterize drought at regional and national levels. These indices cover different types of drought, including meteorological, agricultural, and hydrological drought. By quantifying severity levels and indicating the start and end of drought, these indices aid in various operations such as early warning, monitoring, and contingency planning. The paper discusses the development of drought indices, their performance, and the trend in their evolution. It also emphasizes the importance of combining indices to provide a more comprehensive characterization of drought events. The review concludes by highlighting the need for a universal definition and standardized methods to address the variability in drought types and applications.