The great variability of marine habitats and the species that live there allows the development of organisms with unique characteristics. These represent an excellent source of natural compounds and are therefore interesting in the search for new bioactive molecules. In recent years, many marine-based drugs have been commercialized or are currently under investigation, mainly in the treatment of cancer. This mini-review summarizes the marine-based drugs currently marketed and presents a non-exhaustive list of molecules currently in clinical trials, as monotherapy but also in combination with classical anticancer treatments.