Carotenoids are one of the many bioactive substances found in marine organisms. They are widely found in photosynthesizing bacteria, algae, plants, other fungi, archaea, and animals. Approximately 750 organisms have been found to contain over 1200 different types of carotenoids, of which above 250 are marine in origin. Organisms that perform photosynthesis, like bacteria, algae, plants, and fungi, can synthesize carotenoids de novo. In contrast, animals cannot synthesize carotenoids through this process, so they either accumulate them from food or through modified metabolic reactions. The potential health benefits of marine carotenoids, including zeaxanthin, lutein, fucoxanthin, violaxanthin, neoxanthin, myxol, saproxanthin, siphonaxanthin, bacterioruberin, and others, have been demonstrated in this chapter. These compounds have anti-cancer, anti-ageing, anti-obesity, photo-protective, anti-diabetic, antioxidant, anti-inflammatory, and cardioprotective properties. Carotenoids have significant biological properties that make them suitable for widespread use in commercial applications. Thus, a plethora of recent scientific research has demonstrated the health benefits that carotenoids offer. Moreover, the food, cosmetic, and pharmaceutical industries use carotenoids and their derivatives.