It is well-known that nanofibers are produced in nature, for example, collagen fibrils in tendons andligaments and silk fibroin. Among the variety of natural nanofibers, cellulose microfibrils, which are the majorconstituent of plant cell walls, are the most abundant natural nanofiber on earth. The cellulose microfibrilshave great potential for use as reinforcement in nanocomposites and have attracted a great deal of interestrecently. Many researchers are now tackling the isolation of cellulose nanofibers from plant sources along withtheir efforts to utilize the nano elements. This report reviews the preparation of cellulose nanofibers fromvarious plant sources.Key words : Cellulose