Both gamma and exponential distributions are well-known lifetime distributions. Various extensions of the exponential and gamma distributions were introduced with interesting structural properties. The xgamma distribution is a new introduced lifetime model that was proposed by Sen et al. (2016). Many extensions of the xgamma distribution have been also introduced since 2016 with the hope of finding more flexible models for the lifetime phenomena. In this thesis, we first have a look at the xgamma distribution and its properties and application. Then, we discuss two of its extensions namely the exponentiated xgamma distribution and the quasi xgamma distribution
