Obesity and related co-morbidities are increasing worldwide and pose a serious health problem. Changes in lifestyle and diet would be the best remedies to fight obesity; however, many people will still rely on medical aid. Marine organisms have been prolific in the production of bioactive compounds for many diseases, e.g., cancer, and promise to be an excellent source for natural-derived molecules and novel nutraceuticals. Bioactive compounds with beneficial activities towards obesity have been described from diverse marine organism including marine algae, bacteria, sponges, fungi, crustaceans or fish. This Special Issue will highlight the progress in the following topics: Bioactive compounds for the treatment of obesity and obesity-related co-morbidities (diabetes, fatty liver, hyperlipidemia) from marine organisms; the isolation of novel compounds, the bioactivity screening of marine organisms and the elucidation of molecular mode of action of marine bioactive compounds.