This is the spectacular and comprehensive Revised Third Edition of a book that is the magnum opus of Australian orchid expert David L. Jones. It includes many updates with, most importantly, 30 new species accounts (with photos) added since the publication of the Third Edition in 2019. Therefore this is a new and much improved edition of what has been the best and most authoritative book on the subject since the First Edition was published in 1993. Australia is the world centre of orchid biodiversity, and now that our understanding of the subject has developed over the past 30 years, this Revised Third Edition contains many more species and photos than previously covering more than 1,700 orchid taxa for the first time and much more detailed text than previous editions. It covers more than 130 additional orchid species since the Second Edition, including some which have not yet officially been described. References are now positioned within the main text, distribution maps are included, and there is a more complete and comprehensive introduction. Line drawings help the reader to easily determine the key features of each orchid observed. There are better and clearer layouts for species entries, with greater emphasis placed on conservation aspects, which is important because so many of our orchids are now under threat from all sorts of factors. In short this is a comprehensive guide that will contain correct identification of the orchids (a failure in many other books). It will arguably be the best and most complete work on orchids to be published anywhere in the world.