The investors who sit on the panel in the British show Dragon's Den are called dragons.
The name is part of the programme's branding and explains the title: entrepreneurs enter the den to present their companies to experienced businesspeople who may offer money in return for an ownership stake. The dragons question the pitch, challenge its valuation and decide whether to make an offer.
The terminology differs between international adaptations. Investors are called sharks in the United States version Shark Tank, while the Japanese original used a different title and concept. That variation is a common source of mix-ups in international trivia.
A dragon is not a job title used for every investor in every version of the format. It is specifically the British programme's label for its panel members, whether they are long-serving regulars or temporary guest investors.