Cryptosporidium is an apicomplexan parasite that infects the microvillus border of the gastrointestinal epithelium of various vertebrates, including humans. It causes a wide range of clinical presentations, with pathogenicity varying by species and host factors. In many animals, infections are not clinically significant, but in immunosuppressed individuals or reptiles, it can be chronic and even lethal. Cryptosporidiosis is a common cause of diarrhea in humans, particularly in children under five in developing countries and adults in industrialized nations. Transmission occurs through various routes, including water and person-to-person contact. The lack of clear morphological features and the difficulty in growing the organism in the lab complicate diagnosis and taxonomy. Cryptosporidium taxonomy has been challenging due to the difficulty in defining species, leading to the recognition of multiple species, including C. parvum, C. hominis, C. meleagridis, C. saurophilum, and others. Recent molecular studies have clarified the genetic diversity within the genus, leading to the identification of new species. Cryptosporidium species show host-specific adaptations, and their taxonomy is influenced by host specificity, morphology, and genetic differences. The identification of Cryptosporidium species is crucial for understanding public health implications, as different species can have varying virulence and transmission potential. The taxonomy of Cryptosporidium has evolved significantly, with the recognition of multiple species and the use of molecular methods to validate their existence. Cryptosporidium species in mammals, birds, reptiles, and fish have been identified, with each species showing distinct biological and genetic characteristics. The classification of Cryptosporidium species is essential for understanding their epidemiology and public health impact.Cryptosporidium is an apicomplexan parasite that infects the microvillus border of the gastrointestinal epithelium of various vertebrates, including humans. It causes a wide range of clinical presentations, with pathogenicity varying by species and host factors. In many animals, infections are not clinically significant, but in immunosuppressed individuals or reptiles, it can be chronic and even lethal. Cryptosporidiosis is a common cause of diarrhea in humans, particularly in children under five in developing countries and adults in industrialized nations. Transmission occurs through various routes, including water and person-to-person contact. The lack of clear morphological features and the difficulty in growing the organism in the lab complicate diagnosis and taxonomy. Cryptosporidium taxonomy has been challenging due to the difficulty in defining species, leading to the recognition of multiple species, including C. parvum, C. hominis, C. meleagridis, C. saurophilum, and others. Recent molecular studies have clarified the genetic diversity within the genus, leading to the identification of new species. Cryptosporidium species show host-specific adaptations, and their taxonomy is influenced by host specificity, morphology, and genetic differences. The identification of Cryptosporidium species is crucial for understanding public health implications, as different species can have varying virulence and transmission potential. The taxonomy of Cryptosporidium has evolved significantly, with the recognition of multiple species and the use of molecular methods to validate their existence. Cryptosporidium species in mammals, birds, reptiles, and fish have been identified, with each species showing distinct biological and genetic characteristics. The classification of Cryptosporidium species is essential for understanding their epidemiology and public health impact.