The order Sphaeropleales comprises a diverse and ecologically significant group of green algae within the class Chlorophyceae. Members of the Sphaeropleales display a remarkable variety of morphologies, ranging from unicellular to colonial and filamentous forms. This volume provides a comprehensive overview of 22 families with 74 genera, including detailed descriptions of families, genera, and species, along with identification keys and illustrations. It covers both European and non-European species. The classification presented in this volume is based on a combination of morphological, phylogenetic, and ultrastructural characteristics, which have been carefully considered in the identification process. With a strong focus on taxonomy, ecology, and distinguishing features, this book serves as an essential reference for researchers, students, and enthusiasts seeking to identify and study these algae.