The aim of the present encyclopedia is to introduce the subjects of ecology and environmental management in a concise and organized manner with proper emphasis on fundamentals. The encyclopedia is in 20 chapters of which the first eight deals with the principles of the ecological sciences, and the last twelve chapters are devoted to a discussion of various aspects of environmental management. The topics are arranged according to the new curriculum of the undergraduate courses of the University of Delhi. However, teachers and students of other courses and disciplines may find the encyclopedia quite informative and helpful. An attempt is made here to present the major principles of ecology and environmental management in a lucid and straightforward style. It will be of immense help to have some feed back from those who use this encyclopedia. That may help in future revisions of this encyclopedia.