This book provides a complete and comprehensive account of the orchid flora of Assam. Based on extensive field survey and herbarium study, the authors have recorded 477 taxa (469 species, 3 subspecies, and 5 varieties) belonging to 107 genera from the ambit of the political boundary of Assam. The systematic account of this guide is prepared according to the latest system of orchid classification. Lucid taxonomic keys and descriptions at various hierarchy levels (e.g. Subfamily > Tribe > Genera > Species > variety) have been provided for easy and precise identification of taxon by avoiding confusion. For each species, taxonomic citation followed by a detailed description, phenology, habitat, regional and global distributional data, and regional conservation status etc. has been provided. About 350 taxa are illustrated with 700 coloured photographs and 77 Lankester Composite Dissection Plates, specially prepared from the photographs of dissected floral parts. Besides, 150 species are also illustrated with conventional black and white line drawings. The introductory chapter of this guide deals with the overall morphology of orchids and their growth habits. A general account on Assam is provided to cover physiography, climate, vegetation, and forest types in Assam. Individual chapters are also dedicated to the history of botanical explorations in Assam, various threats to the orchid flora of Assam, their conservation, phytogeography, and endemism. Hope this guidebook will throw light on diversity, distribution, habitat specificity and rarity of wild orchids of Assam and can be helpful for the students, amateur orchid lovers, foresters, field botanists, conservationists and researchers for authentic identification as well as in formulating any pertinent plan for the conservation of threatened orchids of the state. For each species, taxonomic citation followed by details on phenology, habitat, regional and global distribution and regional conservation status has been provided in this book. The book will provide a complete and comprehensive account of the orchid flora of Assam based on extensive field survey. The researchers have studied 469 species, 3 subspecies and 5 different varieties of Orchids for this book.