In Dragon's Den, the investors on the panel are called Dragons.
The name refers to the programme's central image of entrepreneurs entering a den to face powerful businesspeople who may challenge their proposals. Each Dragon can offer money in return for an agreed equity stake, although a pitch may also end without a deal.
The terminology is specific to the British format and its related international adaptations. In the United States version Shark Tank, the panelists are called Sharks instead. This is the most common international mix-up, because both programmes involve entrepreneurs pitching businesses to wealthy investors.
The UK panel has changed over time, with permanent Dragons, guest Dragons and replacement investors appearing in different series. Despite those changes, the collective name “Dragons” has remained part of the show's title and format.