Natural products, with remarkable chemical diversity have played a dominant role in the treatment of human ailments. They are considered as a reservoir of bioactive compounds and are extensively investigated for their therapeutic potentials, most notably in the area of cancer therapy. They cannot function as effective drugs in isolation but they can be converted into a drug through chemical modification. There are a variety of widely-used anticancer agents that originate from natural sources, which are structurally unique and function by novel action mechanisms. Some examples of these natural anticancer agents are camptothecin, irinotecan, vincristine, etoposide and paclitaxel derived from plants; actinomycin D and mitomycin C obtained from bacteria; as well as marine-derived bleomycin. Camptothecin is a naturally occurring quinolone alkaloid isolated from wood and bark of Camptotheca acuminate. It is used as a chemotherapeutic agent for treating leukemia. This book is a compilation of chapters that discuss the most vital concepts and emerging trends in the discovery and development of anti-cancer agents from natural products. It includes contributions of experts and scientists which will provide innovative insights into this area of study.