Sesuvium portulacastrum (L.) L. is a facultative halophyte with great phenotypic plasticity and morphological diversity. It is widely distributed throughout the world and used as a non-model organism to understand the abiotic stress tolerance mechanism in plants. In this chapter, the nomenclature, morphological, cytological, and molecular characteristics of S. portulacastrum are presented to understand its taxonomy, and diversity. Moreover, the halophytic nature and salt stress responses of different Indian clones of this species are reviewed. The plastome and mitochondrial genome analyses further elucidate its molecular taxonomy. Based on nucleotide diversity analysis of two Sesuvium plastomes, probable DNA barcodes have been proposed for the identification of Sesuvium species. This chapter gives a comprehensive understanding of the halophytic nature, ecological significance, and evolutionary dynamics of S. portulacastrum, which can be utilized to select the elite ecotype of Sesuvium for the development of biosaline agriculture.