Presently marine biodiversity is under great threat which is largely due to several unwanted man-made and environmental factors. It therefore warrants urgent conservation and management measures in order to safeguard the existing endangered and critically endangered marine species from further extinction. Awareness has also to be created among sea-goers, marine tourists, recreational fishers and general public to protect such marine species for the betterment of our future generations. Keeping the above in consideration, the present publication is being brought out. It deals with world marine species which are under endangerment, critical endangerment and vulnerable-attaining early endangerment categories. For each species, its common name, classification, habitat, global distribution, diagnostic characters and threats have been elaborately dealt with.