Shark cartilage is a dietary supplement made from the dried and powdered cartilage of a shark; that is, from the tough material that composes a shark's skeleton. Shark cartilage is marketed under a variety of brand names, including Carticin, Cartilade, or BeneFin, and is often explicitly or implicitly marketed as a treatment or preventive for various illnesses including cancer.

There is no scientific evidence that shark cartilage is useful in treating or preventing cancer or other diseases. Controlled trials have shown no benefit to shark cartilage supplements, and shark cartilage contains potentially toxic compounds linked to Alzheimer disease and amyotrophic lateral sclerosis. However, shark cartilage supplements remain popular on the basis of the misconception that sharks do not get cancer, popularized in the 1992 best-selling book Sharks Don't Get Cancer.

Tumors of many kinds, some metastatic, have been found in numerous species of sharks. The first shark tumor was recorded in 1908. Scientists have since discovered 40 benign and cancerous tumors in 18 of the 1,168 species of sharks. Scarcity of studies on shark physiology has perhaps allowed the humor12-myth to be accepted as fact for so many years.

The ongoing consumption of shark cartilage supplements has been linked to a significant decline in shark populations, and the popularity of these supplements has been described as a triumph of pseudoscience and marketing over scientific evaluation.

Detractors also purport that previous beliefs in regards to sharks and cancer have been overturned, as forty-two varieties of cancer have now been discovered in sharks and related species. Also, many opponents feel that non-existent (or even limited) results do not justify the rampant over-fishing of many endangered species of sharks, further threatening their extinction.