The chapter discusses the overview of CO2 sequestration in saline aquifers, and its significance as an important strategy to reduce global warming by minimizing CO2 emissions. It explains fundamental principles like CO2 phase behaviour, interactions with water and rock, and various trapping mechanisms associated with this process. The storage potential of saline aquifers is explained, focusing on key parameters such as storage capacity and CO2 injectivity, which vastly influence their suitability for CO2 storage. A detailed site selection process is also analysed, considering basin characteristics and reservoir parameters, as well as economic and social considerations.