The Phomopsis is an important plant pathogen that causes various symptoms in agricultural crops. This teleomorph is known as Diaporthe. As the spore morphology of different Phomopsis species is highly variable, it is very challenging to confirm the taxonomic rank based on morphological features. DNA sequence-based phylogenetic analysis helped identify the correct taxonomic place of the genus. This chapter highlighted the economic importance, nomenclature and taxonomy, morphological variability, epidemiology and management of the Phomopsis disease.