The order Chaetophorales (sensu Fritsch) is the most fascinating group of green algae occurring in freshwater, marine, and terrestrial habitats. The presence of heterotrichy is the significant character of this order. The first monograph on Indian Chaetophorales was published by P. N. Saxena in the year 1961. The book covered 34 taxa under 13 genera only, thus there was a need for an updated monograph in this line. The present monograph took almost twenty years in the making as Chaetophorales is a difficult group that needs severe attention and patience to identify even up to a generic level. 127 taxa under 30 genera of Chaetophorales (sensu Fritsch 1935) have been included in this book. A taxonomic key for the genera and infraspecific taxa has been given. Over 557 illustrations under 99 drawings and color plates will help the researchers to identify the taxa. The current systematic trend for the placement of each genus has been analysed in a world scenario and in light of modern research. The reader will find an updated and latest account as a guide to identifying the Chaetophorales algae in India.