In heraldry, the dolphin is an ornamental creature in the form of a large fish, the mahi-mahi or dolphinfish, formerly often referred to simply as a dolphin. The heraldic dolphin thus bears little resemblance to the marine mammal of the same name.

The dolphin is found as a charge in early heraldic representations, often with an arched back and fish-like fins. Its attitude is usually shown as either "naiant" – (Old French, now present participle nageant, "swimming") that is, horizontally as though swimming in water – or "hauriant" – that is, shown upright. The term "embowed" is often used, meaning with its tail curved towards the head.

The dolphin is a symbol of the Dauphins of France. Heraldic representations of dolphins also appear in the arms of many British families, and in those of maritime organisations.