The aim of this book is to provide up-to-date information about Coronal Mass Ejections (CMEs), which is one of the most puzzling and outstanding problems in solar physics. Every main sequence star is losing mass, caused by dynamic phenomena in its atmosphere that accelerate plasma or particles beyond the escape speed. Inspecting the Sun, our nearest star, we observe two forms of mass loss: the steady solar wind outflow and the sporadic ejection of large plasma structures, termed coronal mass ejections. In this book author Studied about CMEs; which is one of the main eruptive phenomena from Sun and try to summarized the properties of CMEs during solar cycle 23 and their geospace consequences.